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

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;
    }

}