111. Minimum Depth of Binary Tree

题目：

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.

 

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  Tree Depth-first Search  

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

题解：

求二叉树最短路径长度。依然使用DFS递归求解。

Time Complexity - O(n)， Space Complexity - O(n)。

public class Solution {

    public int minDepth(TreeNode root) {

        if(root == null)

            return 0;

        if(root.left != null && root.right != null)

            return 1 + Math.min(minDepth(root.left), minDepth(root.right));

        else if(root.left == null)

            return 1 + minDepth(root.right);

        else

            return 1 + minDepth(root.left);

    }

}

 

测试：