【LeetCode】543. Diameter of Binary Tree

Given a binary tree, you need to compute the length of the diameter of the tree. The diameter of a binary tree is the length of the longest path between any two nodes in a tree. This path may or may not pass through the root.

Example:
Given a binary tree

          1         / \        2   3       / \           4   5    

Return 3, which is the length of the path [4,2,1,3] or [5,2,1,3].

Note:The length of path between two nodes is represented by the number of edges between them.

题目是求二叉树的任意两个结点之间的最长路径。
后根遍历即可。

class Solution {public:    int maxx=0;    int DFS(TreeNode* root){        if(!root) return 0;        int left=DFS(root->left);        int right=DFS(root->right);        maxx=max(left+right,maxx);        return max(left,right)+1;    }    int diameterOfBinaryTree(TreeNode* root) {        DFS(root);        return maxx;    }};