solution.md

# 最大数

<p>给定一组非负整数 <code>nums</code>，重新排列每个数的顺序（每个数不可拆分）使之组成一个最大的整数。</p>

<p><strong>注意：</strong>输出结果可能非常大，所以你需要返回一个字符串而不是整数。</p>

<p> </p>

<p><strong>示例 1：</strong></p>

<pre>
<strong>输入<code>：</code></strong><code>nums = [10,2]</code>
<strong>输出：</strong><code>"210"</code></pre>

<p><strong>示例 2：</strong></p>

<pre>
<strong>输入<code>：</code></strong><code>nums = [3,30,34,5,9]</code>
<strong>输出：</strong><code>"9534330"</code>
</pre>

<p><strong>示例 3：</strong></p>

<pre>
<strong>输入<code>：</code></strong>nums = [1]
<strong>输出：</strong>"1"
</pre>

<p><strong>示例 4：</strong></p>

<pre>
<strong>输入<code>：</code></strong>nums = [10]
<strong>输出：</strong>"10"
</pre>

<p> </p>

<p><strong>提示：</strong></p>

<ul>
	<li><code>1 <= nums.length <= 100</code></li>
	<li><code>0 <= nums[i] <= 10<sup>9</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
int main()
{
    Solution sol;
    vector<int> nums = {3, 30, 34, 5, 9};
    string res = sol.largestNumber(nums);
    cout << res;

    return 0;
}
```

## 答案
```cpp
class Solution
{
public:
    string largestNumber(vector<int> &nums)
    {
        string ans;
        for (int i = 0; i < nums.size(); i++)
        {
            for (int j = nums.size() - 1; j > i; j--)
            {
                if (to_string(nums[j - 1]) + to_string(nums[j]) > to_string(nums[j]) + to_string(nums[j - 1]))
                {
                    int tmp = nums[j - 1];
                    nums[j - 1] = nums[j];
                    nums[j] = tmp;
                }
            }
            ans += to_string(nums[i]);
        }
        if (ans + "0" == "0" + ans)
            return "0";
        return ans;
    }
};
```
## 选项

### A
```cpp
class Solution
{
public:
    string largestNumber(vector<int> &nums)
    {
        string ans;
        sort(nums.begin(), nums.end(), [](int a, int b)
             { return to_string(a) + to_string(b) > to_string(b) + to_string(a); });
        for (auto it : nums)
        {
            ans += to_string(it);
        }
        return ans[0] == '0' ? "0" : ans;
    }
};
```

### B
```cpp
class Solution
{
public:
    string largestNumber(vector<int> &nums)
    {
        if (*max_element(nums.begin(), nums.end()) == 0)
            return to_string(0);
        vector<string> vec(nums.size());
        for (int i = 0; i < nums.size(); ++i)
            vec[i] = to_string(nums[i]);
        sort(vec.begin(), vec.end(), [](const string &s1, const string &s2)
             { return s1 + s2 > s2 + s1; });
        return accumulate(vec.begin(), vec.end(), string());
    }
};
```

### C
```cpp
class Solution
{
public:
    string largestNumber(vector<int> &nums)
    {
        string res = "";
        int n = nums.size();
        vector<string> tmp;
        for (int i = 0; i < n; i++)
        {
            tmp.push_back(to_string(nums[i]));
        }
        sort(tmp.begin(), tmp.end(), compare);
        for (int i = 0; i < tmp.size(); i++)
        {
            res += tmp[i];
        }
        if ('0' == res[0])
        {
            return "0";
        }
        else
        {
            return res;
        }
    }
};
```