题目描述

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.
Note: A leaf is a node with no children.

Example:

Given binary tree [3,9,20,null,null,15,7],

    3
   / \
  9  20
    /  \
   15   7
return its depth = 3.

题目思路

代码 C++

• 思路一、

/**
 * Definition for a binary tree node.
 * 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 == NULL){
            return 0;
        }   
        
        int Depth_left  = maxDepth(root->left);
        int Depth_right = maxDepth(root->right);
        
        return (Depth_left > Depth_right) ? (Depth_left+1) : (Depth_right+1);
    }
};

总结展望