111. Minimum Depth of Binary Tree

/**
* Definition for a binary tree node.
* 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;
if(root -> left == NULL && root -> right == NULL) return 1;

int dl = minDepth(root -> left);
int dr = minDepth(root -> right);

if(dl == 0) return dr + 1;
if(dr == 0) return dl + 1;

return dl > dr ? dr + 1: dl + 1;
}
};