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.

/**
 * 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) 
    {
        if(root == NULL)
            return 0;
        int l = minDepth(root->left);
        int r = minDepth(root->right);
        if(l==0)
            return r+1;
        if(r==0)
            return l+1;
        return l>r ? (r+1):(l+1);
    }
};