class Solution:
def generateTrees(self, n: int) -> List[TreeNode]:
if not n:
return []
def generateTree(start, end):
if start > end:
return [None]
res = []
for i in range(start, end + 1):
ls = generateTree(start, i - 1)
rs = generateTree(i + 1, end)
for l in ls:
for r in rs:
node = TreeNode(i)
node.left = l
node.right = r
res.append(node)
return res
return generateTree(1, n)
CPP Code:
class Solution {
private:
vector<TreeNode*> generateTrees(int first, int last) {
if (first > last) return { NULL };
vector<TreeNode*> v;
for (int i = first; i <= last; ++i) {
auto lefts = generateTrees(first, i - 1);
auto rights = generateTrees(i + 1, last);
for (auto left : lefts) {
for (auto right : rights) {
v.push_back(new TreeNode(i));
v.back()->left = left;
v.back()->right = right;
}
}
}
return v;
}
public:
vector<TreeNode*> generateTrees(int n) {
if (n <= 0) return {};
return generateTrees(1, n);
}
};
