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.

题目大意：给一个二叉树，计算出任意两个节点中最长的长度并返回结果～

分析：计算每个节点的深度，并在dfs过程中将每个节点左边深度+右边深度的值的最大的值保存在ans中返回～

class Solution {
public:
int diameterOfBinaryTree(TreeNode* root) {
dfs(root);
return ans;
}
private:
int ans = 0;
int dfs(TreeNode* root) {
if (root == NULL) return 0;
int l = dfs(root->left), r = dfs(root->right);
ans = max(ans, l + r);
return max(l, r) + 1;
}
};