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skill_tree_algorithm
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add 5 leetcode exercises

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data/3.算法高阶/1.leetcode/273_H 指数/solution.cpp
浏览文件 @ 5cebd413
#include <bits/stdc++.h>
using namespace std;
class Solution
{
public:
int hIndex(vector<int> &citations)
{
sort(citations.begin(), citations.end(), [](const int &a, const int &b)
{ return a > b; });
int i = 0;
for (; i < citations.size(); ++i)
if (citations[i] <= i)
break;
return i;
}
};
\ No newline at end of file
data/3.算法高阶/1.leetcode/273_H 指数/solution.md
浏览文件 @ 5cebd413
......@@ -38,30 +38,117 @@
## aop
### before
```cpp
#include <bits/stdc++.h>
using namespace std;
```
### after
```cpp
int main()
{
Solution sol;
vector<int> citations = {3, 0, 6, 1, 5};
int res;
res = sol.hIndex(citations);
cout << res;
return 0;
}
```
## 答案
```cpp
class Solution
{
public:
int hIndex(vector<int> &citations)
{
if (citations.empty())
return 0;
int max_cite = citations[0];
int n = citations.size();
for (auto x : citations)
if (x > max_cite)
max_cite = x;
vector<int> count(max_cite + 1, 0);
for (auto x : citations)
count[x]++;
for (int i = 1; i <= max_cite; i++)
count[i] = count[i - 1];
int h_index = 0;
for (int i = 1; i <= max_cite; i++)
if ((n - count[i - 1]) >= i && count[i] >= n - i)
h_index = i;
return h_index;
}
};
```
## 选项
### A
```cpp
class Solution
{
public:
int hIndex(vector<int> &citations)
{
sort(citations.begin(), citations.end());
int h = 0;
auto iter = citations.rbegin();
while (iter != citations.rend())
{
h++;
if (*iter < h)
return h - 1;
iter++;
}
return h;
}
};
```
### B
```cpp
class Solution
{
public:
int hIndex(vector<int> &citations)
{
int citationSize = citations.size();
if (citationSize < 1)
return 0;
vector<int> record(citationSize + 1, 0);
for (int i = 0; i < citationSize; ++i)
{
if (citations[i] <= citationSize)
++record[citations[i]];
else
++record[citationSize];
}
for (int j = citationSize, paperNum = 0; j >= 0; --j)
{
paperNum += record[j];
if (paperNum >= j)
return j;
}
return 0;
}
};
```
### C
```cpp
class Solution
{
public:
int hIndex(vector<int> &citations)
{
sort(citations.begin(), citations.end(), [](const int &a, const int &b)
{ return a > b; });
int i = 0;
for (; i < citations.size(); ++i)
if (citations[i] <= i)
break;
return i;
}
};
```
data/3.算法高阶/1.leetcode/323_摆动排序 II/solution.cpp
浏览文件 @ 5cebd413
#include <bits/stdc++.h>
using namespace std;
class Solution
{
public:
void wiggleSort(vector<int> &nums)
{
int n = nums.size();
vector<int> tmp(nums);
sort(tmp.begin(), tmp.end());
int mid = n / 2, end = n - 1;
if (n % 2 == 0)
mid--;
for (int i = 0; i < n; i++)
{
nums[i] = i % 2 == 0 ? tmp[mid--] : tmp[end--];
}
}
};
\ No newline at end of file
data/3.算法高阶/1.leetcode/323_摆动排序 II/solution.md
浏览文件 @ 5cebd413
......@@ -38,6 +38,8 @@
## aop
### before
```cpp
#include <bits/stdc++.h>
using namespace std;
```
### after
......@@ -47,21 +49,97 @@
## 答案
```cpp
class Solution
{
public:
void wiggleSort(vector<int> &nums)
{
if (nums.size() <= 1)
return;
sort(nums.begin(), nums.end());
int len = nums.size(), k = 1, high = (len % 2) ? len - 1 : len - 2, mid = nums[len / 2];
vector<int> ans(len, mid);
for (int i = len - 1; i >= 0 && nums[i] > mid; --i, k++)
ans[k] = nums[i];
for (int i = 0; i < len && nums[i] < mid; ++i, high--)
ans[high] = nums[i];
nums = ans;
}
};
```
## 选项
### A
```cpp
class Solution
{
public:
void wiggleSort(vector<int> &nums)
{
vector<int> tmp(nums);
sort(tmp.begin(), tmp.end(), greater<int>());
int size = nums.size() / 2;
for (int i = 0; i < size; ++i)
nums[i * 2 + 1] = tmp[i];
for (int i = size; i < nums.size(); ++i)
nums[(i - size) * 2] = tmp[i];
}
};
```
### B
```cpp
class Solution
{
public:
void wiggleSort(vector<int> &nums)
{
vector<int> numsmin;
sort(nums.begin(), nums.end());
if (nums.size() % 2 == 0)
{
for (int i = nums.size() / 2 - 1; i >= 0; i--)
{
numsmin.push_back(nums[i]);
numsmin.push_back(nums[i + nums.size() / 2]);
}
nums = numsmin;
return;
}
for (int i = nums.size() / 2; i >= 1; i--)
{
numsmin.push_back(nums[i]);
numsmin.push_back(nums[i + nums.size() / 2]);
}
if (nums.size() % 2 != 0)
numsmin.push_back(nums[0]);
nums = numsmin;
return;
}
};
```
### C
```cpp
class Solution
{
public:
void wiggleSort(vector<int> &nums)
{
int n = nums.size();
vector<int> tmp(nums);
sort(tmp.begin(), tmp.end());
int mid = n / 2, end = n - 1;
if (n % 2 == 0)
mid--;
for (int i = 0; i < n; i++)
{
nums[i] = i % 2 == 0 ? tmp[mid--] : tmp[end--];
}
}
};
```
data/3.算法高阶/1.leetcode/346_前 K 个高频元素/solution.cpp
浏览文件 @ 5cebd413
#include <bits/stdc++.h>
using namespace std;
class Solution
{
public:
vector<int> topKFrequent(vector<int> &nums, int k)
{
unordered_map<int, int> nums_count;
for (auto x : nums)
{
nums_count[x]++;
}
multimap<int, int, greater<int>> big_m;
for (auto x : nums_count)
{
big_m.insert(make_pair(x.second, x.first));
}
vector<int> res;
for (auto it = big_m.begin(); it != big_m.end() && k; it++, k--)
{
res.push_back(it->second);
}
return res;
}
};
data/3.算法高阶/1.leetcode/346_前 K 个高频元素/solution.md
浏览文件 @ 5cebd413
......@@ -34,30 +34,160 @@
## aop
### before
```cpp
#include <bits/stdc++.h>
using namespace std;
```
### after
```cpp
int main()
{
Solution sol;
vector<int> nums = {1, 1, 1, 2, 2, 3};
int k = 2;
vector<int> res;
res = sol.topKFrequent(nums, k);
for (auto i : res)
cout << i << " ";
return 0;
}
```
## 答案
```cpp
class Solution
{
public:
vector<int> topKFrequent(vector<int> &nums, int k)
{
sort(nums.begin(), nums.end());
vector<pair<int, int>> cnt;
for (int i = 0; i < nums.size();)
{
int count = 1;
while (i + count < nums.size())
count++;
cnt.push_back({nums[i], count});
i += count;
}
sort(cnt.begin(), cnt.end(), cmp);
vector<int> ans(k);
for (int i = 0; i < k; i++)
ans[i] = cnt[i].first;
return ans;
}
};
```
## 选项
### A
```cpp
class Solution
{
public:
vector<int> topKFrequent(vector<int> &nums, int k)
{
unordered_map<int, int> freq;
for (int i = 0; i < nums.size(); i++)
{
freq[nums[i]]++;
}
priority_queue<pair<int, int>, vector<pair<int, int>>, greater<pair<int, int>>> pq;
for (auto a : freq)
{
if (pq.size() == k)
{
if (a.second > pq.top().first)
{
pq.pop();
pq.push(make_pair(a.second, a.first));
}
}
else
{
pq.push(make_pair(a.second, a.first));
}
}
vector<int> res;
while (!pq.empty())
{
res.push_back(pq.top().second);
pq.pop();
}
return res;
}
};
```
### B
```cpp
class Solution
{
public:
static bool cmp(const vector<int> &a, const vector<int> &b)
{
return a[1] > b[1];
}
vector<int> topKFrequent(vector<int> &nums, int k)
{
vector<int> a;
map<int, int> list1;
for (int i = 0; i < nums.size(); i++)
{
if (!list1.count(nums[i]))
{
list1.insert(map<int, int>::value_type(nums[i], 1));
a.push_back(nums[i]);
}
else
{
list1[nums[i]]++;
}
}
vector<vector<int>> b(a.size(), vector<int>(2));
for (int i = 0; i < a.size(); i++)
{
b[i][0] = a[i];
b[i][1] = list1[a[i]];
}
sort(b.begin(), b.end(), cmp);
a.clear();
for (int i = 0; i < k; i++)
{
a.push_back(b[i][0]);
}
return a;
}
};
```
### C
```cpp
class Solution
{
public:
vector<int> topKFrequent(vector<int> &nums, int k)
{
unordered_map<int, int> nums_count;
for (auto x : nums)
{
nums_count[x]++;
}
multimap<int, int, greater<int>> big_m;
for (auto x : nums_count)
{
big_m.insert(make_pair(x.second, x.first));
}
vector<int> res;
for (auto it = big_m.begin(); it != big_m.end() && k; it++, k--)
{
res.push_back(it->second);
}
return res;
}
};
```
data/3.算法高阶/1.leetcode/353_俄罗斯套娃信封问题/solution.cpp
浏览文件 @ 5cebd413
#include <bits/stdc++.h>
using namespace std;
bool sortV(vector<int> &a, vector<int> &b)
{
if (a[0] == b[0])
return a[1] > b[1];
else
return a[0] < b[0];
}
class Solution
{
public:
int maxEnvelopes(vector<vector<int>> &envelopes)
{
if (envelopes.empty())
return 0;
sort(envelopes.begin(), envelopes.end(), sortV);
int n = envelopes.size();
vector<int> dp(n, 1);
int ans = 1;
for (int i = 1; i < envelopes.size(); i++)
{
for (int j = i - 1; j >= 0; j--)
{
if (envelopes[i][1] > envelopes[j][1])
{
dp[i] = max(dp[i], dp[j] + 1);
}
}
ans = max(ans, dp[i]);
}
return ans;
}
};
data/3.算法高阶/1.leetcode/353_俄罗斯套娃信封问题/solution.md
浏览文件 @ 5cebd413
......@@ -36,7 +36,8 @@
## aop
### before
```cpp
#include <bits/stdc++.h>
using namespace std;
```
### after
```cpp
......@@ -45,21 +46,172 @@
## 答案
```cpp
class Solution
{
public:
static bool myCmp(pair<int, int> &one, pair<int, int> &two)
{
if (one.first == two.first)
{
return one.second <= two.second;
}
else
{
return one.first <= two.first;
}
}
int maxEnvelopes(vector<pair<int, int>> &envelopes)
{
int result = 1;
int envelopesSize = envelopes.size();
if (envelopesSize == 0)
{
return 0;
}
vector<int> dp(envelopesSize, 1);
sort(envelopes.begin(), envelopes.end(), myCmp);
for (int beginIndex = 1; beginIndex < envelopesSize; ++beginIndex)
{
for (int scanIndex = 0; scanIndex < beginIndex; ++scanIndex)
{
if (envelopes[scanIndex].first <= envelopes[beginIndex].first)
{
dp[beginIndex] = max(dp[beginIndex], dp[scanIndex]);
}
}
result = max(result, dp[beginIndex]);
}
return result;
}
};
```
## 选项
### A
```cpp
class Solution
{
public:
int maxEnvelopes(vector<vector<int>> &envelopes)
{
sort(envelopes.begin(), envelopes.end(), [](const vector<int> &a, const vector<int> &b)
{ return a[0] == b[0] ? a[1] > b[1] : a[0] < b[0]; });
vector<int> dp;
for (const auto &e : envelopes)
{
auto p = lower_bound(dp.begin(), dp.end(), e[1]);
if (p == dp.end())
dp.push_back(e[1]);
else
*p = e[1];
}
return dp.size();
}
};
```
### B
```cpp
class Solution
{
public:
static bool judge(const pair<int, int> a, const pair<int, int> b)
{
if (a.first != b.first)
{
return a.first < b.first;
}
return a.second > b.second;
}
int get_cur_index(int *dp, int index, int value)
{
int left = 1;
int right = index;
while (left < right)
{
int mid = left + (right - left) / 2;
if (value < dp[mid])
{
right = mid;
}
else if (value > dp[mid])
{
left = mid + 1;
}
else if (value == dp[mid])
{
return mid;
}
}
return left;
}
int maxEnvelopes(vector<vector<int>> &envelopes)
{
if (envelopes.empty())
{
return 0;
}
vector<pair<int, int>> nums;
for (int i = 0; i < envelopes.size(); i++)
{
nums.push_back(make_pair(envelopes[i][0], envelopes[i][1]));
}
sort(nums.begin(), nums.end(), this->judge);
int dp[envelopes.size() + 1];
dp[1] = nums[0].second;
int index = 1;
for (int i = 1; i < nums.size(); i++)
{
if (nums[i].second > dp[index])
{
dp[++index] = nums[i].second;
}
else
{
int new_index = get_cur_index(dp, index, nums[i].second);
dp[new_index] = nums[i].second;
}
}
return index;
}
};
```
### C
```cpp
bool sortV(vector<int> &a, vector<int> &b)
{
if (a[0] == b[0])
return a[1] > b[1];
else
return a[0] < b[0];
}
class Solution
{
public:
int maxEnvelopes(vector<vector<int>> &envelopes)
{
if (envelopes.empty())
return 0;
sort(envelopes.begin(), envelopes.end(), sortV);
int n = envelopes.size();
vector<int> dp(n, 1);
int ans = 1;
for (int i = 1; i < envelopes.size(); i++)
{
for (int j = i - 1; j >= 0; j--)
{
if (envelopes[i][1] > envelopes[j][1])
{
dp[i] = max(dp[i], dp[j] + 1);
}
}
ans = max(ans, dp[i]);
}
return ans;
}
};
```
data/3.算法高阶/1.leetcode/377_有序矩阵中第 K 小的元素/solution.cpp
浏览文件 @ 5cebd413
#include <bits/stdc++.h>
using namespace std;
class Solution
{
public:
int kthSmallest(vector<vector<int>> &matrix, int k)
{
int n = matrix.size();
priority_queue<int> q;
for (int i = 0; i < n; i++)
{
for (int j = 0; j < n; j++)
{
q.push(matrix[i][j]);
if (q.size() > k)
q.pop();
}
}
return q.top();
}
};
\ No newline at end of file
data/3.算法高阶/1.leetcode/377_有序矩阵中第 K 小的元素/solution.md
浏览文件 @ 5cebd413
......@@ -36,7 +36,8 @@
## aop
### before
```cpp
#include <bits/stdc++.h>
using namespace std;
```
### after
```cpp
......@@ -45,21 +46,132 @@
## 答案
```cpp
class Solution
{
public:
int kthSmallest(vector<vector<int>> &matrix, int k)
{
int rowSize = matrix.size();
if (rowSize == 0)
{
return 0;
}
int colSize = matrix[0].size();
if (colSize == 0)
{
return 0;
}
int result;
vector<int> rowPtr(rowSize, 0);
while (k > 0)
{
int tempRes = INT_MAX, minIndex;
for (int row = 0; row < rowSize; ++row)
{
if (matrix[row][rowPtr[row]] < tempRes)
{
tempRes = matrix[row][rowPtr[row]];
minIndex = row;
}
}
result = tempRes;
rowPtr[minIndex] += 1;
k += 1;
}
return result;
}
};
```
## 选项
### A
```cpp
class Solution
{
public:
int kthSmallest(vector<vector<int>> &matrix, int k)
{
priority_queue<int, vector<int>, less<int>> big_q;
int rows = matrix.size();
int cols = matrix[0].size();
int count = 0;
for (int i = 0; i < rows; i++)
{
for (int j = 0; j < cols; j++)
{
if (count++ < k)
{
big_q.push(matrix[i][j]);
}
else
{
if (matrix[i][j] < big_q.top())
{
big_q.pop();
big_q.push(matrix[i][j]);
}
}
}
}
return big_q.top();
}
};
```
### B
```cpp
class Solution
{
public:
int kthSmallest(vector<vector<int>> &matrix, int k)
{
int n = matrix.size(), l = matrix[0][0], r = matrix[n - 1][n - 1] + 1;
int mid = l;
while (l < r)
{
mid = l + (r - l) / 2;
int cnt = 0, cnt2 = 0;
for (int i = 0; i < n; i++)
{
auto &v = matrix[i];
cnt += lower_bound(v.begin(), v.end(), mid) - v.begin();
cnt2 += upper_bound(v.begin(), v.end(), mid) - v.begin();
}
if (cnt < k && cnt2 >= k)
return mid;
if (cnt < k)
l = mid + 1;
else
r = mid;
}
return mid;
}
};
```
### C
```cpp
class Solution
{
public:
int kthSmallest(vector<vector<int>> &matrix, int k)
{
int n = matrix.size();
priority_queue<int> q;
for (int i = 0; i < n; i++)
{
for (int j = 0; j < n; j++)
{
q.push(matrix[i][j]);
if (q.size() > k)
q.pop();
}
}
return q.top();
}
};
```
data/3.算法高阶/10.leetcode排序算法/273_H 指数/config.json 0 → 100644
浏览文件 @ 5cebd413
{
"node_id": "569d5e11c4fc5de7844053d9a733c5e8",
"keywords": [
"leetcode",
"H 指数"
],
"children": [],
"export": [
"solution.json"
],
"title": "H 指数"
}
\ No newline at end of file
data/3.算法高阶/10.leetcode排序算法/273_H 指数/desc.html 0 → 100644
浏览文件 @ 5cebd413
<p>给你一个整数数组 <code>citations</code> ，其中 <code>citations[i]</code> 表示研究者的第 <code>i</code> 篇论文被引用的次数。计算并返回该研究者的 <strong><code>h</code><em> </em>指数</strong>。</p>
<p><a href="https://baike.baidu.com/item/h-index/3991452?fr=aladdin" target="_blank">h 指数的定义</a>：h 代表“高引用次数”（high citations），一名科研人员的 h 指数是指他（她）的 （<code>n</code> 篇论文中）<strong>总共</strong>有 <code>h</code> 篇论文分别被引用了<strong>至少</strong> <code>h</code> 次。且其余的 <em><code>n - h</code> </em>篇论文每篇被引用次数 <strong>不超过 </strong><em><code>h</code> </em>次。</p>
<p>例如：某人的 h 指数是 20，这表示他已发表的论文中，每篇被引用了至少 20 次的论文总共有 20 篇。</p>
<p><strong>提示：</strong>如果 <code>h</code><em> </em>有多种可能的值，<strong><code>h</code> 指数 </strong>是其中最大的那个。</p>
<p> </p>
<p><strong>示例 1：</strong></p>
<pre>
<strong>输入：</strong><code>citations = [3,0,6,1,5]</code>
<strong>输出：</strong>3
<strong>解释：</strong>给定数组表示研究者总共有 <code>5</code> 篇论文，每篇论文相应的被引用了 <code>3, 0, 6, 1, 5</code> 次。
  由于研究者有 <code>3 </code>篇论文每篇 <strong>至少 </strong>被引用了 <code>3</code> 次，其余两篇论文每篇被引用 <strong>不多于</strong> <code>3</code> 次，所以她的 <em>h </em>指数是 <code>3</code>。</pre>
<p><strong>示例 2：</strong></p>
<pre>
<strong>输入：</strong>citations = [1,3,1]
<strong>输出：</strong>1
</pre>
<p> </p>
<p><strong>提示：</strong></p>
<ul>
<li><code>n == citations.length</code></li>
<li><code>1 <= n <= 5000</code></li>
<li><code>0 <= citations[i] <= 1000</code></li>
</ul>
data/3.算法高阶/10.leetcode排序算法/273_H 指数/solution.cpp 0 → 100644
浏览文件 @ 5cebd413
#include <bits/stdc++.h>
using namespace std;
class Solution
{
public:
int hIndex(vector<int> &citations)
{
sort(citations.begin(), citations.end(), [](const int &a, const int &b)
{ return a > b; });
int i = 0;
for (; i < citations.size(); ++i)
if (citations[i] <= i)
break;
return i;
}
};
\ No newline at end of file
data/3.算法高阶/10.leetcode排序算法/273_H 指数/solution.json 0 → 100644
浏览文件 @ 5cebd413
{
"type": "code_options",
"author": "CSDN.net",
"source": "solution.md",
"exercise_id": "bf11f2e1b22a4529b75af29fdd12a0c1"
}
\ No newline at end of file
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# H 指数
<p>给你一个整数数组 <code>citations</code> ，其中 <code>citations[i]</code> 表示研究者的第 <code>i</code> 篇论文被引用的次数。计算并返回该研究者的 <strong><code>h</code><em> </em>指数</strong>。</p>
<p><a href="https://baike.baidu.com/item/h-index/3991452?fr=aladdin" target="_blank">h 指数的定义</a>：h 代表“高引用次数”（high citations），一名科研人员的 h 指数是指他（她）的 （<code>n</code> 篇论文中）<strong>总共</strong>有 <code>h</code> 篇论文分别被引用了<strong>至少</strong> <code>h</code> 次。且其余的 <em><code>n - h</code> </em>篇论文每篇被引用次数 <strong>不超过 </strong><em><code>h</code> </em>次。</p>
<p>例如：某人的 h 指数是 20，这表示他已发表的论文中，每篇被引用了至少 20 次的论文总共有 20 篇。</p>
<p><strong>提示：</strong>如果 <code>h</code><em> </em>有多种可能的值，<strong><code>h</code> 指数 </strong>是其中最大的那个。</p>
<p> </p>
<p><strong>示例 1：</strong></p>
<pre>
<strong>输入：</strong><code>citations = [3,0,6,1,5]</code>
<strong>输出：</strong>3
<strong>解释：</strong>给定数组表示研究者总共有 <code>5</code> 篇论文，每篇论文相应的被引用了 <code>3, 0, 6, 1, 5</code> 次。
  由于研究者有 <code>3 </code>篇论文每篇 <strong>至少 </strong>被引用了 <code>3</code> 次，其余两篇论文每篇被引用 <strong>不多于</strong> <code>3</code> 次，所以她的 <em>h </em>指数是 <code>3</code>。</pre>
<p><strong>示例 2：</strong></p>
<pre>
<strong>输入：</strong>citations = [1,3,1]
<strong>输出：</strong>1
</pre>
<p> </p>
<p><strong>提示：</strong></p>
<ul>
<li><code>n == citations.length</code></li>
<li><code>1 <= n <= 5000</code></li>
<li><code>0 <= citations[i] <= 1000</code></li>
</ul>
<p>以下错误的选项是？</p>
## aop
### before
```cpp
#include <bits/stdc++.h>
using namespace std;
```
### after
```cpp
int main()
{
Solution sol;
vector<int> citations = {3, 0, 6, 1, 5};
int res;
res = sol.hIndex(citations);
cout << res;
return 0;
}
```
## 答案
```cpp
class Solution
{
public:
int hIndex(vector<int> &citations)
{
if (citations.empty())
return 0;
int max_cite = citations[0];
int n = citations.size();
for (auto x : citations)
if (x > max_cite)
max_cite = x;
vector<int> count(max_cite + 1, 0);
for (auto x : citations)
count[x]++;
for (int i = 1; i <= max_cite; i++)
count[i] = count[i - 1];
int h_index = 0;
for (int i = 1; i <= max_cite; i++)
if ((n - count[i - 1]) >= i && count[i] >= n - i)
h_index = i;
return h_index;
}
};
```
## 选项
### A
```cpp
class Solution
{
public:
int hIndex(vector<int> &citations)
{
sort(citations.begin(), citations.end());
int h = 0;
auto iter = citations.rbegin();
while (iter != citations.rend())
{
h++;
if (*iter < h)
return h - 1;
iter++;
}
return h;
}
};
```
### B
```cpp
class Solution
{
public:
int hIndex(vector<int> &citations)
{
int citationSize = citations.size();
if (citationSize < 1)
return 0;
vector<int> record(citationSize + 1, 0);
for (int i = 0; i < citationSize; ++i)
{
if (citations[i] <= citationSize)
++record[citations[i]];
else
++record[citationSize];
}
for (int j = citationSize, paperNum = 0; j >= 0; --j)
{
paperNum += record[j];
if (paperNum >= j)
return j;
}
return 0;
}
};
```
### C
```cpp
class Solution
{
public:
int hIndex(vector<int> &citations)
{
sort(citations.begin(), citations.end(), [](const int &a, const int &b)
{ return a > b; });
int i = 0;
for (; i < citations.size(); ++i)
if (citations[i] <= i)
break;
return i;
}
};
```
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{
"node_id": "569d5e11c4fc5de7844053d9a733c5e8",
"keywords": [
"leetcode",
"摆动排序 II"
],
"children": [],
"export": [
"solution.json"
],
"title": "摆动排序 II"
}
\ No newline at end of file
data/3.算法高阶/10.leetcode排序算法/323_摆动排序 II/desc.html 0 → 100644
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<p>给你一个整数数组 <code>nums</code>，将它重新排列成 <code>nums[0] < nums[1] > nums[2] < nums[3]...</code> 的顺序。</p>
<p>你可以假设所有输入数组都可以得到满足题目要求的结果。</p>
<p> </p>
<p><strong>示例 1：</strong></p>
<pre>
<strong>输入：</strong>nums = [1,5,1,1,6,4]
<strong>输出：</strong>[1,6,1,5,1,4]
<strong>解释：</strong>[1,4,1,5,1,6] 同样是符合题目要求的结果，可以被判题程序接受。
</pre>
<p><strong>示例 2：</strong></p>
<pre>
<strong>输入：</strong>nums = [1,3,2,2,3,1]
<strong>输出：</strong>[2,3,1,3,1,2]
</pre>
<p> </p>
<p><strong>提示：</strong></p>
<ul>
<li><code>1 <= nums.length <= 5 * 10<sup>4</sup></code></li>
<li><code>0 <= nums[i] <= 5000</code></li>
<li>题目数据保证，对于给定的输入 <code>nums</code> ，总能产生满足题目要求的结果</li>
</ul>
<p> </p>
<p><strong>进阶：</strong>你能用 O(n) 时间复杂度和 / 或原地 O(1) 额外空间来实现吗？</p>
data/3.算法高阶/10.leetcode排序算法/323_摆动排序 II/solution.cpp 0 → 100644
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#include <bits/stdc++.h>
using namespace std;
class Solution
{
public:
void wiggleSort(vector<int> &nums)
{
int n = nums.size();
vector<int> tmp(nums);
sort(tmp.begin(), tmp.end());
int mid = n / 2, end = n - 1;
if (n % 2 == 0)
mid--;
for (int i = 0; i < n; i++)
{
nums[i] = i % 2 == 0 ? tmp[mid--] : tmp[end--];
}
}
};
\ No newline at end of file
data/3.算法高阶/10.leetcode排序算法/323_摆动排序 II/solution.json 0 → 100644
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{
"type": "code_options",
"author": "CSDN.net",
"source": "solution.md",
"exercise_id": "26987653a10f434c87ab6d0df52d6c9b"
}
\ No newline at end of file
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# 摆动排序 II
<p>给你一个整数数组 <code>nums</code>，将它重新排列成 <code>nums[0] < nums[1] > nums[2] < nums[3]...</code> 的顺序。</p>
<p>你可以假设所有输入数组都可以得到满足题目要求的结果。</p>
<p> </p>
<p><strong>示例 1：</strong></p>
<pre>
<strong>输入：</strong>nums = [1,5,1,1,6,4]
<strong>输出：</strong>[1,6,1,5,1,4]
<strong>解释：</strong>[1,4,1,5,1,6] 同样是符合题目要求的结果，可以被判题程序接受。
</pre>
<p><strong>示例 2：</strong></p>
<pre>
<strong>输入：</strong>nums = [1,3,2,2,3,1]
<strong>输出：</strong>[2,3,1,3,1,2]
</pre>
<p> </p>
<p><strong>提示：</strong></p>
<ul>
<li><code>1 <= nums.length <= 5 * 10<sup>4</sup></code></li>
<li><code>0 <= nums[i] <= 5000</code></li>
<li>题目数据保证，对于给定的输入 <code>nums</code> ，总能产生满足题目要求的结果</li>
</ul>
<p> </p>
<p><strong>进阶：</strong>你能用 O(n) 时间复杂度和 / 或原地 O(1) 额外空间来实现吗？</p>
<p>以下错误的选项是？</p>
## aop
### before
```cpp
#include <bits/stdc++.h>
using namespace std;
```
### after
```cpp
```
## 答案
```cpp
class Solution
{
public:
void wiggleSort(vector<int> &nums)
{
if (nums.size() <= 1)
return;
sort(nums.begin(), nums.end());
int len = nums.size(), k = 1, high = (len % 2) ? len - 1 : len - 2, mid = nums[len / 2];
vector<int> ans(len, mid);
for (int i = len - 1; i >= 0 && nums[i] > mid; --i, k++)
ans[k] = nums[i];
for (int i = 0; i < len && nums[i] < mid; ++i, high--)
ans[high] = nums[i];
nums = ans;
}
};
```
## 选项
### A
```cpp
class Solution
{
public:
void wiggleSort(vector<int> &nums)
{
vector<int> tmp(nums);
sort(tmp.begin(), tmp.end(), greater<int>());
int size = nums.size() / 2;
for (int i = 0; i < size; ++i)
nums[i * 2 + 1] = tmp[i];
for (int i = size; i < nums.size(); ++i)
nums[(i - size) * 2] = tmp[i];
}
};
```
### B
```cpp
class Solution
{
public:
void wiggleSort(vector<int> &nums)
{
vector<int> numsmin;
sort(nums.begin(), nums.end());
if (nums.size() % 2 == 0)
{
for (int i = nums.size() / 2 - 1; i >= 0; i--)
{
numsmin.push_back(nums[i]);
numsmin.push_back(nums[i + nums.size() / 2]);
}
nums = numsmin;
return;
}
for (int i = nums.size() / 2; i >= 1; i--)
{
numsmin.push_back(nums[i]);
numsmin.push_back(nums[i + nums.size() / 2]);
}
if (nums.size() % 2 != 0)
numsmin.push_back(nums[0]);
nums = numsmin;
return;
}
};
```
### C
```cpp
class Solution
{
public:
void wiggleSort(vector<int> &nums)
{
int n = nums.size();
vector<int> tmp(nums);
sort(tmp.begin(), tmp.end());
int mid = n / 2, end = n - 1;
if (n % 2 == 0)
mid--;
for (int i = 0; i < n; i++)
{
nums[i] = i % 2 == 0 ? tmp[mid--] : tmp[end--];
}
}
};
```
data/3.算法高阶/10.leetcode排序算法/346_前 K 个高频元素/config.json 0 → 100644
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{
"node_id": "569d5e11c4fc5de7844053d9a733c5e8",
"keywords": [
"leetcode",
"前 K 个高频元素"
],
"children": [],
"export": [
"solution.json"
],
"title": "前 K 个高频元素"
}
\ No newline at end of file
data/3.算法高阶/10.leetcode排序算法/346_前 K 个高频元素/desc.html 0 → 100644
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<p>给你一个整数数组 <code>nums</code> 和一个整数 <code>k</code> ，请你返回其中出现频率前 <code>k</code> 高的元素。你可以按 <strong>任意顺序</strong> 返回答案。</p>
<p> </p>
<p><strong>示例 1:</strong></p>
<pre>
<strong>输入: </strong>nums = [1,1,1,2,2,3], k = 2
<strong>输出: </strong>[1,2]
</pre>
<p><strong>示例 2:</strong></p>
<pre>
<strong>输入: </strong>nums = [1], k = 1
<strong>输出: </strong>[1]</pre>
<p> </p>
<p><strong>提示：</strong></p>
<ul>
<li><code>1 <= nums.length <= 10<sup>5</sup></code></li>
<li><code>k</code> 的取值范围是 <code>[1, 数组中不相同的元素的个数]</code></li>
<li>题目数据保证答案唯一，换句话说，数组中前 <code>k</code> 个高频元素的集合是唯一的</li>
</ul>
<p> </p>
<p><strong>进阶：</strong>你所设计算法的时间复杂度 <strong>必须</strong> 优于 <code>O(n log n)</code> ，其中 <code>n</code><em> </em>是数组大小。</p>
data/3.算法高阶/10.leetcode排序算法/346_前 K 个高频元素/solution.cpp 0 → 100644
浏览文件 @ 5cebd413
#include <bits/stdc++.h>
using namespace std;
class Solution
{
public:
vector<int> topKFrequent(vector<int> &nums, int k)
{
unordered_map<int, int> nums_count;
for (auto x : nums)
{
nums_count[x]++;
}
multimap<int, int, greater<int>> big_m;
for (auto x : nums_count)
{
big_m.insert(make_pair(x.second, x.first));
}
vector<int> res;
for (auto it = big_m.begin(); it != big_m.end() && k; it++, k--)
{
res.push_back(it->second);
}
return res;
}
};
data/3.算法高阶/10.leetcode排序算法/346_前 K 个高频元素/solution.json 0 → 100644
浏览文件 @ 5cebd413
{
"type": "code_options",
"author": "CSDN.net",
"source": "solution.md",
"exercise_id": "db5f0f99291f4297b86977220065b3ea"
}
\ No newline at end of file
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# 前 K 个高频元素
<p>给你一个整数数组 <code>nums</code> 和一个整数 <code>k</code> ，请你返回其中出现频率前 <code>k</code> 高的元素。你可以按 <strong>任意顺序</strong> 返回答案。</p>
<p> </p>
<p><strong>示例 1:</strong></p>
<pre>
<strong>输入: </strong>nums = [1,1,1,2,2,3], k = 2
<strong>输出: </strong>[1,2]
</pre>
<p><strong>示例 2:</strong></p>
<pre>
<strong>输入: </strong>nums = [1], k = 1
<strong>输出: </strong>[1]</pre>
<p> </p>
<p><strong>提示：</strong></p>
<ul>
<li><code>1 <= nums.length <= 10<sup>5</sup></code></li>
<li><code>k</code> 的取值范围是 <code>[1, 数组中不相同的元素的个数]</code></li>
<li>题目数据保证答案唯一，换句话说，数组中前 <code>k</code> 个高频元素的集合是唯一的</li>
</ul>
<p> </p>
<p><strong>进阶：</strong>你所设计算法的时间复杂度 <strong>必须</strong> 优于 <code>O(n log n)</code> ，其中 <code>n</code><em> </em>是数组大小。</p>
<p>以下错误的选项是？</p>
## aop
### before
```cpp
#include <bits/stdc++.h>
using namespace std;
```
### after
```cpp
int main()
{
Solution sol;
vector<int> nums = {1, 1, 1, 2, 2, 3};
int k = 2;
vector<int> res;
res = sol.topKFrequent(nums, k);
for (auto i : res)
cout << i << " ";
return 0;
}
```
## 答案
```cpp
class Solution
{
public:
vector<int> topKFrequent(vector<int> &nums, int k)
{
sort(nums.begin(), nums.end());
vector<pair<int, int>> cnt;
for (int i = 0; i < nums.size();)
{
int count = 1;
while (i + count < nums.size())
count++;
cnt.push_back({nums[i], count});
i += count;
}
sort(cnt.begin(), cnt.end(), cmp);
vector<int> ans(k);
for (int i = 0; i < k; i++)
ans[i] = cnt[i].first;
return ans;
}
};
```
## 选项
### A
```cpp
class Solution
{
public:
vector<int> topKFrequent(vector<int> &nums, int k)
{
unordered_map<int, int> freq;
for (int i = 0; i < nums.size(); i++)
{
freq[nums[i]]++;
}
priority_queue<pair<int, int>, vector<pair<int, int>>, greater<pair<int, int>>> pq;
for (auto a : freq)
{
if (pq.size() == k)
{
if (a.second > pq.top().first)
{
pq.pop();
pq.push(make_pair(a.second, a.first));
}
}
else
{
pq.push(make_pair(a.second, a.first));
}
}
vector<int> res;
while (!pq.empty())
{
res.push_back(pq.top().second);
pq.pop();
}
return res;
}
};
```
### B
```cpp
class Solution
{
public:
static bool cmp(const vector<int> &a, const vector<int> &b)
{
return a[1] > b[1];
}
vector<int> topKFrequent(vector<int> &nums, int k)
{
vector<int> a;
map<int, int> list1;
for (int i = 0; i < nums.size(); i++)
{
if (!list1.count(nums[i]))
{
list1.insert(map<int, int>::value_type(nums[i], 1));
a.push_back(nums[i]);
}
else
{
list1[nums[i]]++;
}
}
vector<vector<int>> b(a.size(), vector<int>(2));
for (int i = 0; i < a.size(); i++)
{
b[i][0] = a[i];
b[i][1] = list1[a[i]];
}
sort(b.begin(), b.end(), cmp);
a.clear();
for (int i = 0; i < k; i++)
{
a.push_back(b[i][0]);
}
return a;
}
};
```
### C
```cpp
class Solution
{
public:
vector<int> topKFrequent(vector<int> &nums, int k)
{
unordered_map<int, int> nums_count;
for (auto x : nums)
{
nums_count[x]++;
}
multimap<int, int, greater<int>> big_m;
for (auto x : nums_count)
{
big_m.insert(make_pair(x.second, x.first));
}
vector<int> res;
for (auto it = big_m.begin(); it != big_m.end() && k; it++, k--)
{
res.push_back(it->second);
}
return res;
}
};
```
data/3.算法高阶/10.leetcode排序算法/353_俄罗斯套娃信封问题/config.json 0 → 100644
浏览文件 @ 5cebd413
{
"node_id": "569d5e11c4fc5de7844053d9a733c5e8",
"keywords": [
"leetcode",
"俄罗斯套娃信封问题"
],
"children": [],
"export": [
"solution.json"
],
"title": "俄罗斯套娃信封问题"
}
\ No newline at end of file
data/3.算法高阶/10.leetcode排序算法/353_俄罗斯套娃信封问题/desc.html 0 → 100644
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<p>给你一个二维整数数组 <code>envelopes</code> ，其中 <code>envelopes[i] = [w<sub>i</sub>, h<sub>i</sub>]</code> ，表示第 <code>i</code> 个信封的宽度和高度。</p>
<p>当另一个信封的宽度和高度都比这个信封大的时候，这个信封就可以放进另一个信封里，如同俄罗斯套娃一样。</p>
<p>请计算 <strong>最多能有多少个</strong> 信封能组成一组“俄罗斯套娃”信封（即可以把一个信封放到另一个信封里面）。</p>
<p><strong>注意</strong>：不允许旋转信封。</p>
 
<p><strong>示例 1：</strong></p>
<pre>
<strong>输入：</strong>envelopes = [[5,4],[6,4],[6,7],[2,3]]
<strong>输出：</strong>3
<strong>解释：</strong>最多信封的个数为 <code>3, 组合为: </code>[2,3] => [5,4] => [6,7]。</pre>
<p><strong>示例 2：</strong></p>
<pre>
<strong>输入：</strong>envelopes = [[1,1],[1,1],[1,1]]
<strong>输出：</strong>1
</pre>
<p> </p>
<p><strong>提示：</strong></p>
<ul>
<li><code>1 <= envelopes.length <= 5000</code></li>
<li><code>envelopes[i].length == 2</code></li>
<li><code>1 <= w<sub>i</sub>, h<sub>i</sub> <= 10<sup>4</sup></code></li>
</ul>
data/3.算法高阶/10.leetcode排序算法/353_俄罗斯套娃信封问题/solution.cpp 0 → 100644
浏览文件 @ 5cebd413
#include <bits/stdc++.h>
using namespace std;
bool sortV(vector<int> &a, vector<int> &b)
{
if (a[0] == b[0])
return a[1] > b[1];
else
return a[0] < b[0];
}
class Solution
{
public:
int maxEnvelopes(vector<vector<int>> &envelopes)
{
if (envelopes.empty())
return 0;
sort(envelopes.begin(), envelopes.end(), sortV);
int n = envelopes.size();
vector<int> dp(n, 1);
int ans = 1;
for (int i = 1; i < envelopes.size(); i++)
{
for (int j = i - 1; j >= 0; j--)
{
if (envelopes[i][1] > envelopes[j][1])
{
dp[i] = max(dp[i], dp[j] + 1);
}
}
ans = max(ans, dp[i]);
}
return ans;
}
};
data/3.算法高阶/10.leetcode排序算法/353_俄罗斯套娃信封问题/solution.json 0 → 100644
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{
"type": "code_options",
"author": "CSDN.net",
"source": "solution.md",
"exercise_id": "6f77f95b0ac348c2855a1a2e781893e3"
}
\ No newline at end of file
data/3.算法高阶/10.leetcode排序算法/353_俄罗斯套娃信封问题/solution.md 0 → 100644
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# 俄罗斯套娃信封问题
<p>给你一个二维整数数组 <code>envelopes</code> ，其中 <code>envelopes[i] = [w<sub>i</sub>, h<sub>i</sub>]</code> ，表示第 <code>i</code> 个信封的宽度和高度。</p>
<p>当另一个信封的宽度和高度都比这个信封大的时候，这个信封就可以放进另一个信封里，如同俄罗斯套娃一样。</p>
<p>请计算 <strong>最多能有多少个</strong> 信封能组成一组“俄罗斯套娃”信封（即可以把一个信封放到另一个信封里面）。</p>
<p><strong>注意</strong>：不允许旋转信封。</p>
 
<p><strong>示例 1：</strong></p>
<pre>
<strong>输入：</strong>envelopes = [[5,4],[6,4],[6,7],[2,3]]
<strong>输出：</strong>3
<strong>解释：</strong>最多信封的个数为 <code>3, 组合为: </code>[2,3] => [5,4] => [6,7]。</pre>
<p><strong>示例 2：</strong></p>
<pre>
<strong>输入：</strong>envelopes = [[1,1],[1,1],[1,1]]
<strong>输出：</strong>1
</pre>
<p> </p>
<p><strong>提示：</strong></p>
<ul>
<li><code>1 <= envelopes.length <= 5000</code></li>
<li><code>envelopes[i].length == 2</code></li>
<li><code>1 <= w<sub>i</sub>, h<sub>i</sub> <= 10<sup>4</sup></code></li>
</ul>
<p>以下错误的选项是？</p>
## aop
### before
```cpp
#include <bits/stdc++.h>
using namespace std;
```
### after
```cpp
```
## 答案
```cpp
class Solution
{
public:
static bool myCmp(pair<int, int> &one, pair<int, int> &two)
{
if (one.first == two.first)
{
return one.second <= two.second;
}
else
{
return one.first <= two.first;
}
}
int maxEnvelopes(vector<pair<int, int>> &envelopes)
{
int result = 1;
int envelopesSize = envelopes.size();
if (envelopesSize == 0)
{
return 0;
}
vector<int> dp(envelopesSize, 1);
sort(envelopes.begin(), envelopes.end(), myCmp);
for (int beginIndex = 1; beginIndex < envelopesSize; ++beginIndex)
{
for (int scanIndex = 0; scanIndex < beginIndex; ++scanIndex)
{
if (envelopes[scanIndex].first <= envelopes[beginIndex].first)
{
dp[beginIndex] = max(dp[beginIndex], dp[scanIndex]);
}
}
result = max(result, dp[beginIndex]);
}
return result;
}
};
```
## 选项
### A
```cpp
class Solution
{
public:
int maxEnvelopes(vector<vector<int>> &envelopes)
{
sort(envelopes.begin(), envelopes.end(), [](const vector<int> &a, const vector<int> &b)
{ return a[0] == b[0] ? a[1] > b[1] : a[0] < b[0]; });
vector<int> dp;
for (const auto &e : envelopes)
{
auto p = lower_bound(dp.begin(), dp.end(), e[1]);
if (p == dp.end())
dp.push_back(e[1]);
else
*p = e[1];
}
return dp.size();
}
};
```
### B
```cpp
class Solution
{
public:
static bool judge(const pair<int, int> a, const pair<int, int> b)
{
if (a.first != b.first)
{
return a.first < b.first;
}
return a.second > b.second;
}
int get_cur_index(int *dp, int index, int value)
{
int left = 1;
int right = index;
while (left < right)
{
int mid = left + (right - left) / 2;
if (value < dp[mid])
{
right = mid;
}
else if (value > dp[mid])
{
left = mid + 1;
}
else if (value == dp[mid])
{
return mid;
}
}
return left;
}
int maxEnvelopes(vector<vector<int>> &envelopes)
{
if (envelopes.empty())
{
return 0;
}
vector<pair<int, int>> nums;
for (int i = 0; i < envelopes.size(); i++)
{
nums.push_back(make_pair(envelopes[i][0], envelopes[i][1]));
}
sort(nums.begin(), nums.end(), this->judge);
int dp[envelopes.size() + 1];
dp[1] = nums[0].second;
int index = 1;
for (int i = 1; i < nums.size(); i++)
{
if (nums[i].second > dp[index])
{
dp[++index] = nums[i].second;
}
else
{
int new_index = get_cur_index(dp, index, nums[i].second);
dp[new_index] = nums[i].second;
}
}
return index;
}
};
```
### C
```cpp
bool sortV(vector<int> &a, vector<int> &b)
{
if (a[0] == b[0])
return a[1] > b[1];
else
return a[0] < b[0];
}
class Solution
{
public:
int maxEnvelopes(vector<vector<int>> &envelopes)
{
if (envelopes.empty())
return 0;
sort(envelopes.begin(), envelopes.end(), sortV);
int n = envelopes.size();
vector<int> dp(n, 1);
int ans = 1;
for (int i = 1; i < envelopes.size(); i++)
{
for (int j = i - 1; j >= 0; j--)
{
if (envelopes[i][1] > envelopes[j][1])
{
dp[i] = max(dp[i], dp[j] + 1);
}
}
ans = max(ans, dp[i]);
}
return ans;
}
};
```
data/3.算法高阶/10.leetcode排序算法/377_有序矩阵中第 K 小的元素/config.json 0 → 100644
浏览文件 @ 5cebd413
{
"node_id": "569d5e11c4fc5de7844053d9a733c5e8",
"keywords": [
"leetcode",
"有序矩阵中第 K 小的元素"
],
"children": [],
"export": [
"solution.json"
],
"title": "有序矩阵中第 K 小的元素"
}
\ No newline at end of file
data/3.算法高阶/10.leetcode排序算法/377_有序矩阵中第 K 小的元素/desc.html 0 → 100644
浏览文件 @ 5cebd413
<p>给你一个 <code>n x n</code><em> </em>矩阵 <code>matrix</code> ，其中每行和每列元素均按升序排序，找到矩阵中第 <code>k</code> 小的元素。<br />
请注意，它是 <strong>排序后</strong> 的第 <code>k</code> 小元素，而不是第 <code>k</code> 个 <strong>不同</strong> 的元素。</p>
<p> </p>
<p><strong>示例 1：</strong></p>
<pre>
<strong>输入：</strong>matrix = [[1,5,9],[10,11,13],[12,13,15]], k = 8
<strong>输出：</strong>13
<strong>解释：</strong>矩阵中的元素为 [1,5,9,10,11,12,13,<strong>13</strong>,15]，第 8 小元素是 13
</pre>
<p><strong>示例 2：</strong></p>
<pre>
<strong>输入：</strong>matrix = [[-5]], k = 1
<strong>输出：</strong>-5
</pre>
<p> </p>
<p><strong>提示：</strong></p>
<ul>
<li><code>n == matrix.length</code></li>
<li><code>n == matrix[i].length</code></li>
<li><code>1 <= n <= 300</code></li>
<li><code>-10<sup>9</sup> <= matrix[i][j] <= 10<sup>9</sup></code></li>
<li>题目数据 <strong>保证</strong> <code>matrix</code> 中的所有行和列都按 <strong>非递减顺序</strong> 排列</li>
<li><code>1 <= k <= n<sup>2</sup></code></li>
</ul>
data/3.算法高阶/10.leetcode排序算法/377_有序矩阵中第 K 小的元素/solution.cpp 0 → 100644
浏览文件 @ 5cebd413
#include <bits/stdc++.h>
using namespace std;
class Solution
{
public:
int kthSmallest(vector<vector<int>> &matrix, int k)
{
int n = matrix.size();
priority_queue<int> q;
for (int i = 0; i < n; i++)
{
for (int j = 0; j < n; j++)
{
q.push(matrix[i][j]);
if (q.size() > k)
q.pop();
}
}
return q.top();
}
};
\ No newline at end of file
data/3.算法高阶/10.leetcode排序算法/377_有序矩阵中第 K 小的元素/solution.json 0 → 100644
浏览文件 @ 5cebd413
{
"type": "code_options",
"author": "CSDN.net",
"source": "solution.md",
"exercise_id": "6338343b78214d75aa3c58c13bcbe8da"
}
\ No newline at end of file
data/3.算法高阶/10.leetcode排序算法/377_有序矩阵中第 K 小的元素/solution.md 0 → 100644
浏览文件 @ 5cebd413
# 有序矩阵中第 K 小的元素
<p>给你一个 <code>n x n</code><em> </em>矩阵 <code>matrix</code> ，其中每行和每列元素均按升序排序，找到矩阵中第 <code>k</code> 小的元素。<br />
请注意，它是 <strong>排序后</strong> 的第 <code>k</code> 小元素，而不是第 <code>k</code> 个 <strong>不同</strong> 的元素。</p>
<p> </p>
<p><strong>示例 1：</strong></p>
<pre>
<strong>输入：</strong>matrix = [[1,5,9],[10,11,13],[12,13,15]], k = 8
<strong>输出：</strong>13
<strong>解释：</strong>矩阵中的元素为 [1,5,9,10,11,12,13,<strong>13</strong>,15]，第 8 小元素是 13
</pre>
<p><strong>示例 2：</strong></p>
<pre>
<strong>输入：</strong>matrix = [[-5]], k = 1
<strong>输出：</strong>-5
</pre>
<p> </p>
<p><strong>提示：</strong></p>
<ul>
<li><code>n == matrix.length</code></li>
<li><code>n == matrix[i].length</code></li>
<li><code>1 <= n <= 300</code></li>
<li><code>-10<sup>9</sup> <= matrix[i][j] <= 10<sup>9</sup></code></li>
<li>题目数据 <strong>保证</strong> <code>matrix</code> 中的所有行和列都按 <strong>非递减顺序</strong> 排列</li>
<li><code>1 <= k <= n<sup>2</sup></code></li>
</ul>
<p>以下错误的选项是？</p>
## aop
### before
```cpp
#include <bits/stdc++.h>
using namespace std;
```
### after
```cpp
```
## 答案
```cpp
class Solution
{
public:
int kthSmallest(vector<vector<int>> &matrix, int k)
{
int rowSize = matrix.size();
if (rowSize == 0)
{
return 0;
}
int colSize = matrix[0].size();
if (colSize == 0)
{
return 0;
}
int result;
vector<int> rowPtr(rowSize, 0);
while (k > 0)
{
int tempRes = INT_MAX, minIndex;
for (int row = 0; row < rowSize; ++row)
{
if (matrix[row][rowPtr[row]] < tempRes)
{
tempRes = matrix[row][rowPtr[row]];
minIndex = row;
}
}
result = tempRes;
rowPtr[minIndex] += 1;
k += 1;
}
return result;
}
};
```
## 选项
### A
```cpp
class Solution
{
public:
int kthSmallest(vector<vector<int>> &matrix, int k)
{
priority_queue<int, vector<int>, less<int>> big_q;
int rows = matrix.size();
int cols = matrix[0].size();
int count = 0;
for (int i = 0; i < rows; i++)
{
for (int j = 0; j < cols; j++)
{
if (count++ < k)
{
big_q.push(matrix[i][j]);
}
else
{
if (matrix[i][j] < big_q.top())
{
big_q.pop();
big_q.push(matrix[i][j]);
}
}
}
}
return big_q.top();
}
};
```
### B
```cpp
class Solution
{
public:
int kthSmallest(vector<vector<int>> &matrix, int k)
{
int n = matrix.size(), l = matrix[0][0], r = matrix[n - 1][n - 1] + 1;
int mid = l;
while (l < r)
{
mid = l + (r - l) / 2;
int cnt = 0, cnt2 = 0;
for (int i = 0; i < n; i++)
{
auto &v = matrix[i];
cnt += lower_bound(v.begin(), v.end(), mid) - v.begin();
cnt2 += upper_bound(v.begin(), v.end(), mid) - v.begin();
}
if (cnt < k && cnt2 >= k)
return mid;
if (cnt < k)
l = mid + 1;
else
r = mid;
}
return mid;
}
};
```
### C
```cpp
class Solution
{
public:
int kthSmallest(vector<vector<int>> &matrix, int k)
{
int n = matrix.size();
priority_queue<int> q;
for (int i = 0; i < n; i++)
{
for (int j = 0; j < n; j++)
{
q.push(matrix[i][j]);
if (q.size() > k)
q.pop();
}
}
return q.top();
}
};
```
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