Minimum Depth of Binary Tree

Minimum Depth of Binary Tree

• 描述

  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.

• 思路

  求二叉树的最小深度，根据定义：当最小深度为根节点到最近的结点的距离;
  关于二叉树的问题我们不难想到用递归实现，对于递归，最重要的是找到递归的结束条件和递归体，我们应采取的思想是化简，如何理解了？我们可以将树的左右结点现象成一个节点，这样我们只需考虑三种情况，该结点为空，左右孩子分别为空时：

• AC代码

/** * Definition for a binary tree node. * public class TreeNode { *     int val; *     TreeNode left; *     TreeNode right; *     TreeNode(int x) { val = x; } * } */public class Solution {    public int minDepth(TreeNode root) {       if(root==null)            return 0;        if(root.right==null)             return minDepth(root.left)+1;        if(root.left==null)            return minDepth(root.right)+1;        int minLeft=minDepth(root.left);        int minRight=minDepth(root.right);        return (minLeft<minRight?minLeft:minRight)+1;    }}