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.

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给定一个二叉树，找出其最大深度。 

二叉树的深度为根节点到最远叶子节点的距离。

如果二叉树为空，则深度为0 

如果不为空，分别求左子树的深度和右子树的深度，去最大的再加1，因为根节点深度是1，要加进去。

/**
* 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 (NULL == root)
return 0;
int l = maxDepth(root->left);
int r = maxDepth(root->right);

return l > r ? l + 1:r+1;

}
};

/**
* 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 height(TreeNode* root) {
if(root==NULL)
return 0;
else{
int l=height(root->left);
int r=height(root->right);
return 1+((l>r)?l:r);
}
}
int maxDepth(TreeNode* root) {
if (NULL == root)
return 0;
int l = height(root->left);
int r = height(root->right);

return l > r ? l + 1:r+1;

}
};