Leetcode104

Maximum Depth of Binary Tree:
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],
return its depth = 3.

Solution:

#include <iostream>

using namespace std;


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;

        return max( maxDepth( root->right), maxDepth( root->left)) + 1;


    }
};

总结： 用了递归的思想。