[leetcode][**] 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.

Attention: 

from root to leaf distance 

               1

        2

   3        5

4

this distance is till 3 not 1. should find the nearest leaf!!

My Code:

int minDepth(TreeNode *root) {
        if(root == NULL) return 0;
        else if(root->left == NULL && root->right == NULL)
            return 1;
        else if(root->left == NULL && root->right != NULL)
            return 1 + minDepth(root->right);
        else if(root->right == NULL && root->left != NULL)
            return 1 + minDepth(root->left);
        else
            return 1 + std::min(minDepth(root->left), minDepth(root->right));
        }