vector<TreeNode*> generateTreesDFS(int start, int end)
{
vector<TreeNode*> subTree;
if (start>end)
{
subTree.push_back(NULL);
}
else
{
for (int i=start; i<=end; i++)
{
vector<TreeNode*> leftSubTree = generateTreesDFS(start, i - 1);
vector<TreeNode*> rightSubTree = generateTreesDFS(i + 1, end);
for (int j = 0; j < leftSubTree.size(); ++j)
for (int k = 0; k < rightSubTree.size(); ++k)
{
TreeNode *node = new TreeNode(i);
node->left = (leftSubTree)[j];
node->right = (rightSubTree)[k];
subTree.push_back(node);
}
}
}
return subTree;
}
vector<TreeNode*>* generateTreesDFS(int start, int end) {
vector<TreeNode*> *subTree = new vector<TreeNode*>();
if(start > end) {
subTree->push_back(NULL);
}else {
for(int i = start; i <= end; ++i) {
vector<TreeNode*> *leftSubTree = generateTreesDFS(start, i-1);
vector<TreeNode*> *rightSubTree = generateTreesDFS(i+1, end);
for(int j = 0; j < leftSubTree->size(); ++j) {
for(int k = 0; k < rightSubTree->size(); ++k) {
TreeNode *node = new TreeNode(i);
node->left = (*leftSubTree)[j];
node->right = (*rightSubTree)[k];
subTree->push_back(node);
}
}
}
}
return subTree;
}
vector<TreeNode*> generateTrees(int n) {
return *generateTreesDFS(1, n);
}
vector<TreeNode*> generateTrees(int n)
{
if (n == 0) return {};
return generateTreesDFS(1,n);
}
