104. Maximum Depth of Binary Tree

问题
Given the root of a binary tree, return its maximum depth.

A binary tree’s maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.

递归,每次返回左子节点和右子节点中较大的结果+1。
当节点为null时返回0。

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

BFS搜索,每次倾倒出队列里所有的元素并将level+1。
搜索完毕返回level。

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class Solution {
public int maxDepth(TreeNode root) {
if(root == null){
return 0;
}
Queue<TreeNode> q = new LinkedList();
q.offer(root);
int level = 0;
while(!q.isEmpty()){
int size = q.size();
for (int i = 0; i < size; i++){
TreeNode curr = q.poll();
if(curr.left!=null){q.offer(curr.left);}
if(curr.right!=null){q.offer(curr.right);}
}
level++;
}
return level;
}
}
Author

Xander

Posted on

2022-04-13

Updated on

2022-04-13

Licensed under

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