qq_19450921的博客

class Solution {// 从叶子节点往上遍历，最终剩下的是结果public List findMinHeightTrees(int n, int[][] edges) {List res = new ArrayList<>();if (n == 1) {res.add(0);return res;}int[] degree = new int[n];Map<Integer, Set> map = new HashMap<>();for (i

DFS:/*// Definition for a Node.class Node { public int val; public List<Node> children; public Node() {} public Node(int _val,List<Node> _children) { val = _va...

最近在刷搜索，DFS，BFS，backtracking的题。如果你是初学者，建议多看一些模版，然后一定动手写。我在上学的时候，对这些代码就只是看过，过了脑子，等自己写的时候，会发现很多问题。最近更新的代码DFS的一个套路，BFS的一个套路，然后等遇到具体问题具体分析。这道题莫名的看了半天solution，又取层数，又判断距离的，没想明白。最后直接写BFS也就过了。Given a matri...

睡醒解决了个bug。In a given 2D binary array A, there are two islands. (An island is a 4-directionally connected group of 1s not connected to any other 1s.)Now, we may change 0s to 1s so as to connect the ...

又写一道好老好老的题。第一次见到是。。。。四年前了吧，老得我都觉得自己没啥长进了。正能量正能量！Example 1:Input:beginWord = “hit”,endWord = “cog”,wordList = [“hot”,“dot”,“dog”,“lot”,“log”,“cog”]Output: 5Explanation: As one shortest transfor...

For example, this binary tree [1,2,2,3,4,4,3] is symmetric:1/ 2 2/ \ / 3 4 4 3But the following [1,2,2,null,3,null,3] is not:1/ 2 2\ 3 3想到的是层遍历每一行，再判断是否是回文。Runtime: 1 ms, fas...