[LeetCode]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.

思路：

树的递归遍历演化，从最简单的深度为1的树想，一个节点 maxdep=1。

父节点是左右两个孩子中最大的深度+1

/**
* Definition for binary tree
* public class TreeNode {
*     int val;
*     TreeNode left;
*     TreeNode right;
*     TreeNode(int x) { val = x; }
* }
*/
public class Solution {
public int maxDepth(TreeNode root) {
int leftdepth,rightdepth;
if(root==null){
return 0;
}
if(root.left==null && root.right==null){
return 1;
}
leftdepth=maxDepth(root.left)+1;
rightdepth=maxDepth(root.right)+1;
if(leftdepth>rightdepth)
return leftdepth;
else return rightdepth;
}
}

简化方法（来源互联网）

if(root == NULL) return 0;
return max(maxDepth(root.left), maxDepth(root.right))+1;