边去递归边记录
import java.util.*;
/*
* public class TreeNode {
* int val = 0;
* TreeNode left = null;
* TreeNode right = null;
* public TreeNode(int val) {
* this.val = val;
* }
* }
*/
public class Solution {
/**
* 代码中的类名、方法名、参数名已经指定,请勿修改,直接返回方法规定的值即可
*
*
* @param root TreeNode类
* @return int整型
*/
int ans = 0;
public int diameterOfBinaryTree (TreeNode root) {
// write code here
dfs(root);
return ans;
}
int dfs(TreeNode root){
if(root== null){
return 0;
}
int l = dfs(root.left);
int r = dfs(root.right);
ans = Math.max(l+r,ans);
return Math.max(l,r)+1;
}
}