LeetCode https://leetcode.cn/problems/symmetric-tree/ /** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeN...

LeetCode https://leetcode.cn/problems/invert-binary-tree/ Recursive /** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode righ...

LeetCode https://leetcode.cn/problems/binary-tree-level-order-traversal/ /** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode ...

LeetCode https://leetcode.cn/problems/maximum-depth-of-binary-tree/ /** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right...

LeetCode https://leetcode.cn/problems/binary-tree-inorder-traversal/   10 == root   /   \           5     15         /   \   /   \         2     7 12   20   ...

LeetCode https://leetcode.cn/problems/first-unique-character-in-a-string/ class Solution { public int firstUniqChar(String s) { HashMap<Character, Integer> map = new HashMap<...

LeetCode https://leetcode.cn/problems/lru-cache/ 这是个啥玩意？？ https://en.wikipedia.org/wiki/Cache_replacement_policies#LRU 题目描述 请你设计并实现一个满足LRU (最近最少使用) 缓存 约束的数据结构。 实现 LRUCache 类： LRUCache(int c...

LeetCode https://leetcode.cn/problems/group-anagrams/ 字母异位词分组 class Solution { public List<List<String>> groupAnagrams(String[] strs) { Map<String, List<String&g...

Leetcode https://leetcode.cn/problems/two-sum/ class Solution { public int[] twoSum(int[] nums, int target) { Map<Integer, Integer> hashtable = new HashMap<Integer, Integer>...

读了很有感触，贴文章到这里存档 走一步再走一步（2016人教版） 默顿·亨特 那是在费城，一个酷热的七月天——直到56年后的今天，我仍能感觉到那种酷热。和我在一起的五个男孩子已经厌倦了玩弹珠，以及用透镜在干树叶上烧洞等游戏，他们正在寻觅其他好玩的事。 一脸雀斑的小内德说到：“嗨！我有主意了。我们很久没去爬悬崖了。” “我们走吧！”有人附和着。然后他们出发了，他们气喘吁吁地一路小跑...