Sum of Distances in Tree An undirected, connected tree with N nodes labelled 0...N-1 and N-1 edges are given. The ith edge connects nodes edges[i][0] and edges[i][1] together. Return a list ans, where ans[i] is the sum of the distances between node i…

An undirected, connected tree with N nodes labelled 0...N-1 and N-1 edges are given. The ith edge connects nodes edges[i][0] and edges[i][1] together. Return a list ans, where ans[i] is the sum of the distances between node i and all other nodes. Exa…

LeetCode刷题记录 传送门 Description An undirected, connected treewith N nodes labelled 0...N-1 and N-1 edges are given. The ith edge connects nodes edges[i][0] and edges[i][1] together. Return a list ans, where ans[i] is the sum of the distances between nod…

There is an undirected connected tree with n nodes labeled from 0 to n - 1 and n - 1 edges. You are given the integer n and the array edges where edges[i] = [ai, bi] indicates that there is an edge between nodes ai and bi in the tree. Return an array…

An undirected, connected tree with N nodes labelled 0...N-1 and N-1 edges are given. The ith edge connects nodes edges[i][0]and edges[i][1] together. Return a list ans, where ans[i] is the sum of the distances between node i and all other nodes. Exam…

2019-03-28 15:25:43 问题描述: 问题求解: 写过的最好的Hard题之一. 初看本题,很经典的路径和嘛,dfs一遍肯定可以得到某个节点到其他所有节点的距离和.这种算法的时间复杂度是O(n ^ 2).看一下数据量,emmm,果然不行.这个数据量一看就知道只能是O(n)的算法了. 只遍历一遍最多只能得到一个解,因此本题肯定是需要遍历至少两遍的. 在第一遍遍历的时候我们需要保存下两个值,一个是当前节点的subtree的路径总和,一个是当前节点的subtree的总的节点数. 在第二遍遍…

思路: 树形dp. 实现: class Solution { public: void dfs(int root, int p, vector<vector<int>>& G, vector<int>& cnt, vector<int>& res) { for (auto it: G[root]) { if (it == p) continue; dfs(it, root, G, cnt, res); cnt[root] += cnt…

Image Overlap Two images A and B are given, represented as binary, square matrices of the same size.  (A binary matrix has only 0s and 1s as values.) We translate one image however we choose (sliding it left, right, up, or down any number of units),…

Find And Replace in String To some string S, we will perform some replacement operations that replace groups of letters with new ones (not necessarily the same size). Each replacement operation has 3 parameters: a starting index i, a source word x an…

Flipping an Image Given a binary matrix A, we want to flip the image horizontally, then invert it, and return the resulting image. To flip an image horizontally means that each row of the image is reversed.  For example, flipping [1, 1, 0] horizontal…