[LeetCode-104] Maximum Depth of Binary Tree（二叉树最大深度）

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.

【分析】
本题就是求解二叉树的深度：
递归解法：
（1）如果二叉树为空，二叉树的深度为0
（2）如果二叉树不为空，二叉树的深度 = max(左子树深度， 右子树深度) + 1

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 * int val;
 * struct TreeNode *left;
 * struct TreeNode *right;
 * };
 */
int maxDepth(struct TreeNode* root) {
if(root == NULL) // 递归出口
return 0;
int depthLeft = maxDepth(root->left);
int depthRight = maxDepth(root->right);
return depthLeft > depthRight ? (depthLeft + 1) : (depthRight + 1); 
}