问题描述

Given a binary tree, find its maximum depth.

The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.

解决方案

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    int maxDepth(TreeNode *root) {
            if( root == nullptr ) {
                return 0;
            }
            if( root->left == nullptr && root->right == nullptr ) {
                return 1;
            } else if( root->left == nullptr ) {
                return 1 + maxDepth( root->right );
            } else if( root->right == nullptr ) {
                return  1 + maxDepth( root->left );
            } else {
                return 1 + max( maxDepth( root->left ), maxDepth( root->right ) );
            }
    }
};

Maximum Depth of Binary Tree