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111.二叉树的最小深度.java
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111.二叉树的最小深度.java
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/*
* @lc app=leetcode.cn id=111 lang=java
*
* [111] 二叉树的最小深度
*
* https://leetcode-cn.com/problems/minimum-depth-of-binary-tree/description/
*
* algorithms
* Easy (39.56%)
* Likes: 153
* Dislikes: 0
* Total Accepted: 29K
* Total Submissions: 72.4K
* Testcase Example: '[3,9,20,null,null,15,7]'
*
* 给定一个二叉树,找出其最小深度。
*
* 最小深度是从根节点到最近叶子节点的最短路径上的节点数量。
*
* 说明: 叶子节点是指没有子节点的节点。
*
* 示例:
*
* 给定二叉树 [3,9,20,null,null,15,7],
*
* 3
* / \
* 9 20
* / \
* 15 7
*
* 返回它的最小深度 2.
*
*/
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
class Solution {
public int minDepth(TreeNode root) {
if (root == null) {
return 0;
}
int l = minDepth(root.left);
int r = minDepth(root.right);
if (l == 0 && r == 0) {
return 1;
}
if (l == 0) {
return r + 1;
}
if (r == 0) {
return l + 1;
}
return Math.min(l, r) + 1;
}
}