題目鏈接：https://leetcode.com/PRoblems/minimum-depth-of-binary-tree/?tab=Description

題目描述:

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：這道題和 LeetCode 104. Maximum Depth of Binary Tree相反， 可以用同樣的思路，但是要注意的是，當(dāng)前節(jié)點(diǎn)左子樹或者右子樹為空時(shí)需要判斷一下

代碼：

/** * Definition for a binary tree node. * struct TreeNode { *     int val; *     TreeNode *left; *     TreeNode *right; *     TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */class Solution {public:    int minDepth(TreeNode* root) {        if(root==NULL)            return 0 ;        int depth1=minDepth(root->left);        int depth2=minDepth(root->right);        if(depth1==0&&depth2==0)            return 1;        else if(depth1==0&&depth2!=0)            return depth2+1;        else if(depth1!=0&&depth2==0)            return depth1+1;        else            return depth1<depth2?depth1+1:depth2+1;            }};