leetcode - Unique Binary Search Trees II

/**
* Definition for binary tree
* struct TreeNode {
*     int val;
*     TreeNode *left;
*     TreeNode *right;
*     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
vector <TreeNode *> generateTrees(int min, int max){
if (min>max){
TreeNode * tmp = NULL;
return vector<TreeNode*>(1,tmp);
}
vector<TreeNode *> rlt;
for (int i=min; i<=max; i++){
vector<TreeNode*> left_nodes = generateTrees(min, i-1);
int lsize = left_nodes.size();
vector<TreeNode*> right_nodes = generateTrees(i+1,max);
int rsize = right_nodes.size();
for (int j=0; j<lsize; j++)
for (int k=0; k<rsize; k++){
TreeNode * node = new TreeNode(i);
node->left = left_nodes[j];
node->right = right_nodes[k];
rlt.push_back(node);
}
}
return rlt;
}
vector<TreeNode *> generateTrees(int n) {
// IMPORTANT: Please reset any member data you declared, as
// the same Solution instance will be reused for each test case.
return generateTrees(1,n);
}
};