[Leetcode 104]求二叉树的深度Depth of BinaryTree

【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.

Note: A leaf is a node with no children.

Example:

Given binary tree [3,9,20,null,null,15,7],

    3
   / \
  9  20
    /  \
   15   7

return its depth = 3.

 

【思路】

递归，1+Math.max(maxDepth(root.left),maxDepth(root.right));

 

【解答】

class Solution {

    public int maxDepth(TreeNode root) {

        if(root==null)

            return 0;

        return 1+Math.max(maxDepth(root.left),maxDepth(root.right));

    }

}

 

【其他定义】

 * Definition for a binary tree node.

 * public class TreeNode {

 *     int val;

 *     TreeNode left;

 *     TreeNode right;

 *     TreeNode(int x) { val = x; }

 * }

/** * Definition for a binary tree node. * public class TreeNode { *     int val; *     TreeNode left; *     TreeNode right; *     TreeNode(int x) { val = x; } * } */class Solution {    public int maxDepth(TreeNode root) {        if(root==null)            return 0;        return 1+Math.max(maxDepth(root.left),maxDepth(root.right));    }    }