Minimum Depth of Binary Tree

Description:

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.

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

PS:  注意题目的说明，当结点root的其中一个孩子为空时，应当返回另一个孩子的最小深度，而不能直接返回1（1+0）。