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…

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. Exam…

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…

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…

Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum. For example: Given the below binary tree andsum = 22, 5 / \ 4 8 / / \ 11 13 4 / \ \ 7 2 1 return true…

CodeChef Sum of distances(分治) 题目大意 有一排点,每个点 i 向 \(i + 1, i + 2, i + 3\) 分别连价值为 \(a_i,b_i,c_i\) 的有向边,问两两间最短路之和 数据范围 \(1 \le n \le 10^5\) 解题思路 这种题已经从新颖变成套路了(唉) 考虑分治,很容易发现如果断掉连续的三个点那么图就不再联通,我们从中间找三个点,然后分别向两边跑最短路,设点 i 到三点最短距离为 \(x_1,x_2,x_3\),三点到 j 最短距离为…

题目如下: Given the root of a binary tree, the level of its root is 1, the level of its children is 2, and so on. Return the smallest level X such that the sum of all the values of nodes at level X is maximal. Example 1: Input: [1,7,0,7,-8,null,null] Out…