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提交 bde8702c 编写于 作者: L liu13
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20190102

上级 9d71221d
隐藏空白更改
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Showing with 287 addition and 6 deletion
code/lc105.java
浏览文件 @ bde8702c
......@@ -8,21 +8,34 @@ package code;
* Tips：思路记一下，自己想不起来
*/
public class lc105 {
public class TreeNode {
public static class TreeNode {
int val;
TreeNode left;
TreeNode right;
TreeNode(int x) { val = x; }
}
public TreeNode buildTree(int[] preorder, int[] inorder) {
public static void main(String[] args) {
int[] preorder = {3,9,20,15,7};
int[] inorder = {9,3,15,20,7};
buildTree(preorder,inorder);
}
public TreeNode Recursion(int[] preorder, int[] inorder, int val, int start, int end){ //start,end代表在inorder上搜索的范围
public static TreeNode buildTree(int[] preorder, int[] inorder) {
return recursion(preorder, inorder, 0, 0, inorder.length-1);
}
public static TreeNode recursion(int[] preorder, int[] inorder, int pre_index, int start, int end){ //start,end代表在inorder上搜索的范围
if(start>end || start >inorder.length)
return null;
for (int i = 0; i < ; i++) {
TreeNode tn = new TreeNode(preorder[pre_index]);
int in_index = 0;
for (int i = 0; i <= end; i++) {
if(preorder[pre_index]==inorder[i])
in_index = i;
}
tn.left = recursion(preorder, inorder, pre_index+1, start, in_index-1);
tn.right = recursion(preorder, inorder, pre_index+in_index-start+1, in_index+1, end); //注意右孩子节点index参数
return tn;
}
}
code/lc114.java 0 → 100644
浏览文件 @ bde8702c
package code;
/*
* 114. Flatten Binary Tree to Linked List
* 题意：二叉树转链表
* 难度：Medium
* 分类：Tree, Depth-first Search
* 思路：就是节点间连接换一下，理清思路就行了，类似中序遍历
* Tips：
*/
public class lc114 {
public class TreeNode {
int val;
TreeNode left;
TreeNode right;
TreeNode(int x) { val = x; }
}
public void flatten(TreeNode root) {
if(root==null)
return;
flatten(root.left);
flatten(root.right);
TreeNode origin_r = root.right;
root.right = root.left; //右节点替换为左节点
TreeNode right_leaf = root;
while(right_leaf.right!=null){ //右节点遍历到最后，把左节点接上
right_leaf = right_leaf.right;
}
right_leaf.right = origin_r;
root.left = null; //别忘了把left设成null
}
}
code/lc121.java 0 → 100644
浏览文件 @ bde8702c
package code;
/*
* 121. Best Time to Buy and Sell Stock
* 题意：股票买卖1次，最大利润
* 难度：Easy
* 分类：Arryas, Dynamic Programming
*/
public class lc121 {
public int maxProfit(int[] prices) {
int min = prices[0];if(prices.length==0)
return 0;
int res =0;
for (int i = 1; i < prices.length ; i++) {
res = Math.max(prices[i]-min,res);
if(prices[i]<min)
min = prices[i];
}
return res;
}
}
code/lc136.java 0 → 100644
浏览文件 @ bde8702c
package code;
/*
* 136. Single Number
* 题意：找出数组中单一的数
* 难度：Easy
* 分类：Hash Table, Bit Maniputation
* 思路：两种巧妙方法：1.异或 2. set以后sum*2 - sum
* Tips：
*/
import java.util.ArrayList;
import java.util.HashSet;
import java.util.Set;
public class lc136 {
public static void main(String[] args) {
int[] nums = {2,2,1};
System.out.println(singleNumber(nums));
System.out.println(singleNumber2(nums));
}
public static int singleNumber(int[] nums) {
int res = nums[0];
for (int i = 1; i < nums.length ; i++) {
res = res ^ nums[i];
}
return res;
}
public static int singleNumber2(int[] nums) {
Set<Integer> s = new HashSet();
int sum = 0;
int sum2 = 0;
for (int i = 0; i < nums.length ; i++) {
sum += nums[i];
s.add(nums[i]);
}
for(Integer i : s){
sum2 += i;
}
return 2*sum2 - sum;
}
}
code/lc139.java 0 → 100644
浏览文件 @ bde8702c
package code;
/*
* 139. Word Break
* 题意：是否能够分词
* 难度：Medium
* 分类：Dynamic Programming
* 思路：动态规划
* Tips：巧妙的方法，防止了复杂的操作，通过遍历之前计算出来的结果
*/
import java.util.List;
public class lc139 {
public boolean wordBreak(String s, List<String> wordDict) {
boolean[] dp = new boolean[s.length()+1];
dp[0] = true;
for (int i = 1; i < dp.length ; i++) {
for (int j = 0; j < i ; j++) { //遍历之前计算出来的结果
if( dp[j]==true && wordDict.contains(s.substring(j,i)))
dp[i] = true;
}
}
return dp[s.length()+1];
}
}
code/lc141.java 0 → 100644
浏览文件 @ bde8702c
package code;
/*
* 141. Linked List Cycle
* 题意：链表是否有换
* 难度：Easy
* 分类：Linked List, Two Pointers
* 思路：快慢指针
*/
public class lc141 {
public class ListNode {
int val;
ListNode next;
ListNode(int x) { val = x; }
}
public boolean hasCycle(ListNode head) {
if(head==null)
return false;
ListNode faster = head;
ListNode slow = head;
while( faster.next!=null && faster.next.next!=null){ //注意判断条件，slow一定不等于null，不用判断了
slow = slow.next;
faster = faster.next.next;
if(slow==faster)
return true;
}
return false;
}
}
readme.md 0 → 100644
浏览文件 @ bde8702c
LeetCode Top 100 Liked Questions
===
<img src="img/readme.png"></a>
The user's favorite 100 problems are very classic. If you are a newbie, this is the best way to get started with leetcode.
Language: Java
*If there was something wrong, you can new a issue.
Welcome to improve this project with me.*
---
用户最喜欢的100道题都是很经典的问题，是新手入门 leetcode 的最好方式。**每道题在代码头部都添加了我的解题思路和想法，希望对你有用**。
语言: Java
*相关问题可以直接提交一个issue，欢迎和我一起完善这个项目*
---
### Top 100 Liked Questions
| \# | Problems | Difficulty | Solution |
|----|----------|-----------|------|
| 001 | [Two_Sum](https://leetcode.com/problems/two-sum/) | Easy | [Java](./src/lc1.java)
| 002 | [Add Two Numbers](https://leetcode.com/problems/add-two-numbers/) |Medium| [Java](./src/lc2.java)
| 003 | [Longest Substring Without Repeating Characters](https://leetcode.com/problems/longest-substring-without-repeating-characters/) | Medium | [Java]
| 004 | [Median of Two Sorted Arrays](https://leetcode.com/problems/median-of-two-sorted-arrays) | Hard | [Java]
| 005 | [Longest Palindromic Substring](https://leetcode.com/problems/longest-palindromic-substring/) |Medium|[Java]
| 010 | [Regular Expression Matching](https://leetcode.com/problems/regular-expression-matching/) | Hard | [Java]
| 011 | [Container With Most Water](https://leetcode.com/problems/container-with-most-water/) |Medium| [Java]
| 015 | [3Sum](https://leetcode.com/problems/3sum/) |Medium| [Java]
| 017 | [Letter Combinations of a Phone Number](https://leetcode.com/problems/letter-combinations-of-a-phone-number/) |Medium| [Java]
| 019 | [Remove Nth Node From End of List](https://leetcode.com/problems/remove-nth-node-from-end-of-list/) | Easy | [Java]
| 020 | [Valid Parentheses](https://leetcode.com/problems/valid-parentheses/) | Easy | [Java]
| 021 | [Merge Two Sorted Lists](https://leetcode.com/problems/merge-two-sorted-lists/) | Easy | [Java]
| 022 | [Generate Parentheses](https://leetcode.com/problems/generate-parentheses/) |Medium| [Java]
| 023 | [Merge k Sorted Lists](https://leetcode.com/problems/merge-k-sorted-lists/) | Hard | [Java]
| 032 | [Longest Valid Parentheses](https://leetcode.com/problems/longest-valid-parentheses/) | Hard | [Java]
| 033 | [Search in Rotated Sorted Array](https://leetcode.com/problems/search-in-rotated-sorted-array/) |Medium| [Java]
| 034 | [Search for a Range](https://leetcode.com/problems/search-for-a-range/) |Medium| [Java]
| 035 | [Search Insert Position](https://leetcode.com/problems/search-insert-position/) |Medium| [Java]
| 039 | [Combination Sum](https://leetcode.com/problems/combination-sum/) |Medium| [Java]
| 042 | [Trapping Rain Water](https://leetcode.com/problems/trapping-rain-water/) | Hard | [Java]
| 046 | [Permutations](https://leetcode.com/problems/permutations/) |Medium| [Java] |
| 048 | [Rotate Image](https://leetcode.com/problems/rotate-image/) |Medium| [Java]
| 049 | [Group Anagrams](https://leetcode.com/problems/anagrams/)|Medium| [Java]
| 053 | [Maximum Subarray](https://leetcode.com/problems/maximum-subarray/) |Medium| [Java]
| 055 | [Jump Game](https://leetcode.com/problems/jump-game/) |Medium| [Java]
| 056 | [Merge Intervals](https://leetcode.com/problems/merge-intervals/) |Medium| [Java]
| 062 | [Unique Paths](https://leetcode.com/problems/unique-paths/) |Medium| [Java]
| 064 | [Minimum Path Sum](https://leetcode.com/problems/minimum-path-sum/) |Medium| [Java]
| 070 | [Climbing Stairs](https://leetcode.com/problems/climbing-stairs/) | Easy | [Java]
| 072 | [Edit Distance](https://leetcode.com/problems/edit-distance/) | Hard | [Java]
| 075 | [Sort Colors](https://leetcode.com/problems/sort-colors/)|Medium| [Java]
| 076 | [Minimum Window Substring](https://leetcode.com/problems/minimum-window-substring) | Hard| [Java]
| 078 | [Subsets](https://leetcode.com/problems/subsets/) |Medium| [Java]
| 079 | [Word Search](https://leetcode.com/problems/word-search/)|Medium| [Java]
| 084 | [Largest Rectangle in Histogram](https://leetcode.com/problems/largest-rectangle-in-histogram) | Hard | [Java]
| 085 | [Maximal Rectangle](https://leetcode.com/problems/maximal-rectangle) | Hard |[Java]
| 094 | [Binary Tree Inorder Traversal](https://leetcode.com/problems/binary-tree-inorder-traversal/) |Medium| [Java]
| 096 | [Unique Binary Search Trees](https://leetcode.com/problems/unique-binary-search-trees/) |Medium| [Java]
| 098 | [Validate Binary Search Tree](https://leetcode.com/problems/validate-binary-search-tree/) |Medium| [Java]
| 100 | [Same Tree](https://leetcode.com/problems/same-tree/) | Easy | [Java]
| 101 | [Symmetric Tree](https://leetcode.com/problems/symmetric-tree/) | Easy | [Java]
| 102 | [Binary Tree Level Order Traversal](https://leetcode.com/problems/binary-tree-level-order-traversal/) | Easy | [Java]
| 104 | [Maximum Depth of Binary Tree](https://leetcode.com/problems/maximum-depth-of-binary-tree/) | Easy | [Java]
| 105 | [Construct Binary Tree from Preorder and Inorder Traversal](https://leetcode.com/problems/construct-binary-tree-from-preorder-and-inorder-traversal/) |Medium| [Java]
| 114 | [Flatten Binary Tree to Linked List](https://leetcode.com/problems/flatten-binary-tree-to-linked-list/) |Medium| [Java]
| 121 | [Best Time to Buy and Sell Stock](https://leetcode.com/problems/best-time-to-buy-and-sell-stock/) | Easy | [Java]
| 124 | [Binary Tree Maximum Path Sum](https://leetcode.com/problems/binary-tree-maximum-path-sum/) | Hard | [Java]
| 128 | [Longest Consecutive Sequence](https://leetcode.com/problems/longest-consecutive-sequence/) | Hard | [Java]
| 136 | [Single Number](https://leetcode.com/problems/single-number) | Easy | [Java]
| 139 | [Word Break](https://leetcode.com/problems/word-break/) |Medium| [Java]
| 141 | [Linked List Cycle](https://leetcode.com/problems/linked-list-cycle/) | Easy | [Java]
| 142 | [Linked List Cycle II](https://leetcode.com/problems/linked-list-cycle-ii/) |Medium| [Java]
| 146 | [LRU Cache](https://leetcode.com/problems/lru-cache/) | Hard | [Java] |
| 148 | [Sort List](https://leetcode.com/problems/sort-list/) |Medium| [Java]
| 152 | [Maximum Product Subarray](https://leetcode.com/problems/maximum-product-subarray/) |Medium| [Java]
| 155 | [Min Stack](https://leetcode.com/problems/min-stack/) | Easy | [Java]
| 160 | [Intersection of Two Linked Lists](https://leetcode.com/problems/intersection-of-two-linked-lists/) | Easy | [Java]
| 169 | [Majority Element](https://leetcode.com/problems/majority-element/) | Easy | [Java]
| 198 | [House Robber](https://leetcode.com/problems/house-robber/) | Easy | [Java]
| 200 | [Number of Islands](https://leetcode.com/problems/number-of-islands/) |Medium| [Java]
| 206 | [Reverse Linked List](https://leetcode.com/problems/reverse-linked-list/) | Easy |[Java]
| 207 | [Course Schedule](https://leetcode.com/problems/course-schedule/) |Medium|[Java]
| 208 | [Implement Trie (Prefix Tree)](https://leetcode.com/problems/implement-trie-prefix-tree/) |Medium| [Java]
| 215 | [Kth Largest Element in an Array](https://leetcode.com/problems/kth-largest-element-in-an-array/) |Medium| [Java]
| 218 | [Subarray Sum Equals K](https://leetcode.com/problems/subarray-sum-equals-k) | Hard |[Java]
| 221 | [Maximal Square](https://leetcode.com/problems/maximal-square/) |Medium| [Java]
| 226 | [Invert Binary Tree](https://leetcode.com/problems/invert-binary-tree/) | Easy | [Java]
| 234 | [Palindrome Linked List](https://leetcode.com/problems/palindrome-linked-list/) | Easy | [Java]
| 236 | [Lowest Common Ancestor of a Binary Tree](https://leetcode.com/problems/lowest-common-ancestor-of-a-binary-tree/) |Medium| [Java]
| 238 | [Product of Array Except Self](https://leetcode.com/problems/product-of-array-except-self/) |Medium| [Java]
| 239 | [Sliding Window Maximum](https://leetcode.com/problems/sliding-window-maximum/) | Hard | [Java] |
| 240 | [Search a 2D Matrix II](https://leetcode.com/problems/search-a-2d-matrix-ii/) |Medium| [Java]
| 279 | [Perfect Squares](https://leetcode.com/problems/perfect-squares/) |Medium| [Java]
| 283 | [Move Zeroes](https://leetcode.com/problems/move-zeroes/)| Easy | [Java]
| 287 | [Find the Duplicate Number](https://leetcode.com/problems/find-the-duplicate-number/) | Hard | [Java]
| 297 | [Serialize and Deserialize Binary Tree](https://leetcode.com/problems/serialize-and-deserialize-binary-tree/) | Hard | [Java]
| 300 | [Longest Increasing Subsequence](https://leetcode.com/problems/longest-increasing-subsequence/) |Medium| [Java]
| 309 | [Best Time to Buy and Sell Stock with Cooldown](https://leetcode.com/problems/best-time-to-buy-and-sell-stock-with-cooldown/) |Medium| [Java]
| 312 | [Burst Balloons](https://leetcode.com/problems/burst-balloons/) | Hard | [Java]
| 322 | [Coin Change](https://leetcode.com/problems/coin-change/)|Medium| [Java]
| 337 | [House Robber III](https://leetcode.com/problems/house-robber-iii/) |Medium| [Java]
| 338 | [Counting Bits](https://leetcode.com/problems/counting-bits/) |Medium| [Java]
| 347 | [Top K Frequent Elements](https://leetcode.com/problems/top-k-frequent-elements/) |Medium| [Java]
| 394 | [Decode String](https://leetcode.com/problems/decode-string/) |Medium| [Java]
| 406 | [Queue Reconstruction by Height](https://leetcode.com/problems/queue-reconstruction-by-height/) |Medium| [Java]
| 416 | [Partition Equal Subset Sum](https://leetcode.com/problems/partition-equal-subset-sum/) |Medium| [Java]
| 437 | [Path Sum III](https://leetcode.com/problems/path-sum-iii/) | Easy |[Java]
| 438 | [Find All Anagrams in a String](https://leetcode.com/problems/find-all-anagrams-in-a-string/) | Easy |[Java]
| 448 | [Find All Numbers Disappeared in an Array](https://leetcode.com/problems/find-all-numbers-disappeared-in-an-array/) | Easy | [Java]
| 461 | [Hamming Distance](https://leetcode.com/problems/hamming-distance/) | Easy |[Java]
| 494 | [Target Sum](https://leetcode.com/problems/target-sum/) |Medium|[Java]
| 538 | [Convert BST to Greater Tree](https://leetcode.com/problems/convert-bst-to-greater-tree/description/) | Easy |[Java]
| 543 | [Diameter of Binary Tree](https://leetcode.com/problems/diameter-of-binary-tree/description/) | Easy | [Java]
| 560 | [Subarray Sum Equals K](https://leetcode.com/problems/subarray-sum-equals-k) |Medium| [Java]
| 572 | [Subtree of Another Tree](https://leetcode.com/problems/subtree-of-another-tree/description/) | Easy | [Java]
| 581 | [Shortest Unsorted Continuous Subarray](https://leetcode.com/problems/shortest-unsorted-continuous-subarray/description/) | Easy | [Java]
| 617 | [Merge Two Binary Trees](https://leetcode.com/problems/merge-two-binary-trees/description/) | Easy | [Java]
| 621 | [Task Scheduler](https://leetcode.com/problems/task-scheduler) |Medium| [Java] |
| 647 | [Palindromic Substrings](https://leetcode.com/problems/palindromic-substrings) |Medium|[Java]
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