一:题目

二:上码

/*** Definition for a binary tree node.* public class TreeNode {*     int val;*     TreeNode left;*     TreeNode right;*     TreeNode() {}*     TreeNode(int val) { this.val = val; }*     TreeNode(int val, TreeNode left, TreeNode right) {*         this.val = val;*         this.left = left;*         this.right = right;*     }* }*/
class Solution {/**- 分别求取左右子树的最大高度  求取其和        */  int ans = 0;public int getLenNode(TreeNode root) {if (root == null) return 0;int leftLen = getLenNode(root.left);int rightLen = getLenNode(root.right);int depth = Math.max(leftLen,rightLen) + 1;ans = Math.max(leftLen+rightLen,ans);return  depth;}public int diameterOfBinaryTree(TreeNode root) {getLenNode(root);return ans;}
}