[Leetcode]Minimum Depth of Binary Tree

/** * Definition for binary tree * struct TreeNode { *     int val; *     TreeNode *left; *     TreeNode *right; *     TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */class Solution {public:    int minDepth(TreeNode *root) {        // Start typing your C/C++ solution below        // DO NOT write int main() function        if(root == NULL) return 0;        if(!root->left) return minDepth(root->right) + 1;        if(!root->right) return minDepth(root->left) + 1;        return min(minDepth(root->left), minDepth(root->right)) + 1;    }};