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.

int minDepth(TreeNode *root){    if(root == NULL)        return 0;    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), minDepth(root->right))+1;}