leetCode 111.Minimum Depth of Binary Tree(二叉树最小深度) 解题思路和方法

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：求解根节点到叶子的最小距离。与求树的最大深度类似，只是一个求大，一个求小。

具体代码如下：

/** * 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;        return minDep(0,root);    }        private int minDep(int dep,TreeNode root){        if(root == null){            return dep;        }        int dep1 = minDep(dep+1,root.left);        int dep2 = minDep(dep+1,root.right);        if(dep1 == dep+1){        return dep2;        }        if(dep2 == dep+1){        return dep1;        }        return dep1 > dep2 ? dep2 : dep1;    }}