vector<TreeNode *>* generateTreesHelper(int start, int end, vector<vector<void*> > &dp){
vector<TreeNode*>* res = new vector<TreeNode*>();
if(start > end || start == 0){
res->push_back(NULL);
if(dp[0][0])
delete res;
else
dp[0][0] = res;
return (vector<TreeNode*>*)dp[0][0];
}
if(dp[start][end])
return (vector<TreeNode*>*)dp[start][end];
for(int i = start; i <= end; i++){
vector<TreeNode *> *left = generateTreesHelper(start, i-1, dp);
vector<TreeNode *> *right = generateTreesHelper(i+1, end, dp);
for(int l = 0; l < left->size(); l++){
for(int r = 0; r < right->size(); r++){
TreeNode* node = new TreeNode(i);
node->left = (*left)[l];
node->right = (*right)[r];
res->push_back(node);
}
}
}
dp[start][end] = res;
return res;
}
vector<TreeNode*> generateTreesHelper(int left, int right)
{
vector<TreeNode*> nodes;
if(left>right)
{
nodes.push_back(NULL);
return nodes;
}
for(int k=left; k<=right; k++)
{
vector<TreeNode*> leftnodes=generateTreesHelper(left,k-1);
vector<TreeNode*> rightnodes=generateTreesHelper(k+1,right);
for(int i=0; i<leftnodes.size();i++)
{
for(int j=0; j<rightnodes.size(); j++)
{
TreeNode* node=new TreeNode(k);
node->left=leftnodes[i];
node->right=rightnodes[j];
nodes.push_back(node);
}
}
}
return nodes;
}
vector<TreeNode *> generateTreesHelper(int start, int end){
vector<TreeNode*> res;
if(start > end || start == 0){
res.push_back(NULL);
return res;
}
for(int i = start; i <= end; i++){
vector<TreeNode *> left = generateTreesHelper(start, i-1);
vector<TreeNode *> right = generateTreesHelper(i+1, end);
for(int l = 0; l < left.size(); l++){
for(int r = 0; r < right.size(); r++){
TreeNode* node = new TreeNode(i);
node->left = left[l];
node->right = right[r];
res.push_back(node);
}
}
}
return res;
}
vector<TreeNode *> generateTrees(int n) {
vector<vector<void*> > dp(n + 1, vector<void*>(n + 1, NULL));
vector<TreeNode*> res;
res = *generateTreesHelper(1, n, dp);
for(int i = 0; i <= n; i++){
for(int j = 0; j <= n; j++){
if(dp[i][j])
delete (vector<TreeNode*>*)dp[i][j];
}
}
return res;
}
/**
* @paramn n: An integer
* @return: A list of root
*/
vector<TreeNode *> generateTrees(int n) {
// write your code here
vector<vector<void*> > dp(n+1, vector<void*>(n+1, NULL));
vector<TreeNode*> rtn;
rtn = *generateTreesHelper(1, n, dp);
for(int i = 0; i <= n; i++){
for(int j = 0; j <= n; j++){
if(dp[i][j])
delete (vector<TreeNode*>*)dp[i][j];
}
}
return rtn;
}
/**
* @paramn n: An integer
* @return: A list of root
*/
vector<TreeNode *> generateTrees(int n) {
// write your code here
return generateTreesHelper(1, n);
}
vector<TreeNode *> generateTrees(int n) {
// Start typing your C/C++ solution below
// DO NOT write int main() function
return generateTreesHelper(1,n);
}
vector<TreeNode *> generateTrees(int n) {
return generateTreesHelper(1, n);
}