LeetCode - 543. Diameter of Binary Tree(Binary Tree, Recursion, DFS)*

문제

Given the root of a binary tree, return 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.
The length of a path between two nodes is represented by the number of edges between them.

https://leetcode.com/problems/diameter-of-binary-tree/

Example 1:

Input: root = [1,2,3,4,5]
Output: 3
Explanation: 3 is the length of the path [4,2,1,3] or [5,2,1,3].

Example 2:

Input: root = [1,2]
Output: 1

풀이

class Solution {
    int max;
    public int diameterOfBinaryTree(TreeNode root) {
        countDepth(root);
        return max;
    }
    
    public int countDepth(TreeNode root){
        if(root==null) return 0;
        int left = countDepth(root.left);
        int right = countDepth(root.right);
        // max = (max>left+right)?max:left+right;
        max = Math.max(max,left+right);
        // return 1+(left>right?left:right);
        return 1+Math.max(left,right);
    }
}