DiameterofBinaryTree_543.cpp

/*
~ Author    : leetcode.com/tridib_2003/
~ Problem   : 543. Diameter of Binary Tree
~ Link      : https://leetcode.com/problems/diameter-of-binary-tree/
*/

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    int ans;
    int diameterOfBinaryTree(TreeNode* root) {
        ans = 1;
        depth(root);
        return ans - 1;
    }
    int depth(TreeNode* root) {
        if (root == NULL)
            return 0;
        int l = depth(root->left);
        int r = depth(root->right);
        ans = max(ans, (l + r + 1));
        return max(l, r) + 1;
    }
};