Maximum Depth of Binary Tree

题目：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.

思路：深搜

如果节点为空，返回0,；如果不为空，要看是否左右孩子节点是否存在，不存在直接返回1.
然后剩下有说明至少存在一个，左节点在，就定义left加上1.右节点同样处理。

代码：

/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
//本质上方法一样，只是通过实践竟然不同
class Solution1 {
//https://leetcode.com/problems/maximum-depth-of-binary-tree/
public:
int maxDepth(TreeNode* root) {
if(root==NULL){
return 0;
}
if(root->left==NULL&&root->right==NULL){
return 1;
}

int left=0;
if(root->left){
left=maxDepth(root->left)+1;
}

int right=0;
if(root->right){
right=maxDepth(root->right)+1;
}

return max(left,right);
}
};

class Solution2 {
public:
int count=1;
int maxDepth(TreeNode* root) {
if(root==NULL){
return 0;
}
//int left=maxDepth(root->left);
//int right=maxDepth(root->right);
return max(maxDepth(root->left)+1,maxDepth(root->right)+1);
}
};