leetcode

0 class Solution {

1 TreeNode *duplicate(TreeNode *root) {

2 TreeNode *dup = new TreeNode(root->val);

3 if (root->left) dup->left = duplicate(root->left);

4 if (root->right) dup->right = duplicate(root->right);

5 return dup;

6 }

7

8 vector<TreeNode *> dp[20];

9

10 public:

11 vector<TreeNode *> allPossibleFBT(int n) {

12 if (n % 2 == 0) return {};

13 if (1 == n) return {new TreeNode(0)};

14

15 if (!dp[n].empty()) return dp[n];

16

17 vector<TreeNode *> ret;

18 for (int i = 2; i <= n; i += 2) {

19 auto left = allPossibleFBT(i - 1);

20 auto right = allPossibleFBT(n - i);

21 for (int l = 0; l < left.size(); l++) {

22 for (int r = 0; r < right.size(); r++) {

23 ret.push_back(new TreeNode(0));

24 ret.back()->left = (r == right.size() - 1) ? left[l] : duplicate(left[l]);

25 ret.back()->right = (l == left.size() - 1) ? right[r] : duplicate(right[r]);

26 }

27 }

28 }

29

30 return dp[n] = ret;

31 }

32 };