[LeetCode] Minimum Depth of Binary Tree

链接https://leetcode.com/problems/minimum-depth-of-binary-tree/description/

难度:Easy

题目:111. Minimum Depth of Binary Tree

Given a binary tree, find its minimum depth.

The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node.

翻译:给定一棵二叉树,求它的最小深度。 最小深度是沿着从根节点到最近的叶节点的最短路径的节点的数量。

思路:本题与Maximum Depth of Binary Tree类似,依旧用递归的方法来求解。不过,有个地方要注意一下,左子树或者右子树为空时,我们不能直接让其深度等于0,而要转去求非空的右子树或者左子树的深度。

参考代码

Java

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/**
* 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;
if(root.left == null)
return 1+minDepth(root.right);
if(root.right == null)
return 1+minDepth(root.left);
return 1+Math.min(minDepth(root.left), minDepth(root.right));
}
}