Minimum Depth of Binary Tree

/*

Minimum Depth of Binary Tree

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.

*/
/**
 * 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==NULL && root->right==NULL) return 1;
        if (root->left==NULL) return minDepth(root->right)+1;
        else if (root->right==NULL) return minDepth(root->left)+1;
        else return min(minDepth(root->left)+1,minDepth(root->right)+1);
    }
};