maximun-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.

此题类似二叉树最小深度。

/**

* Definition for binary tree

* public class TreeNode {

*     int val;

*     TreeNode left;

*     TreeNode right;

*     TreeNode(int x) { val = x; }

* }

*/

import java.util.*;

public class Solution {

public int maxDepth(TreeNode root) {

if(root==null)

return 0;

if(root.left==null&&root.right==null)

return 1;

方法一：递归

/*    if(root.left==null)

return maxDepth(root.right)+1;

if(root.right==null)

return maxDepth(root.left)+1;

int left=maxDepth(root.left);

int right=maxDepth(root.right);

return (left>right)?(left+1):(right+1);

*/

//方法二：层序遍历结束，每一层level加一

Queue<TreeNode> q=new LinkedList<>();

q.add(root);

int level=0;

while(!q.isEmpty()){

int size=q.size();

level++;

for(int i=0;i<size;i++){

TreeNode node=q.poll();

if(node.left!=null)

q.add(node.left);

if(node.right!=null)

q.add(node.right);

}

}

return level;

}

}