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.

思路：分别求出左右节点的最小深度，然后返回其中一个较小的深度。

/** * 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.left==null && root.right==null) {            return 1;        }        int leftDepth = 1 + minDepth(root.left);        leftDepth = (leftDepth==1)?Integer.MAX_VALUE:leftDepth;        int rightDepth = 1 + minDepth(root.right);        rightDepth = (rightDepth==1)?Integer.MAX_VALUE:rightDepth;        return (leftDepth<rightDepth)?leftDepth:rightDepth;    }}