894. All Possible Full Binary Trees

 Given an integer n, return a list of all possible full binary trees with n nodes. Each node of each tree in the answer must have Node.val == 0.

Each element of the answer is the root node of one possible tree. You may return the final list of trees in any order.

A full binary tree is a binary tree where each node has exactly 0 or 2 children.

 

Example 1:

Input: n = 7
Output: [[0,0,0,null,null,0,0,null,null,0,0],[0,0,0,null,null,0,0,0,0],[0,0,0,0,0,0,0],[0,0,0,0,0,null,null,null,null,0,0],[0,0,0,0,0,null,null,0,0]]

Example 2:

Input: n = 3
Output: [[0,0,0]]

 

Constraints:

• 1 <= n <= 20

Solution :

	class Solution(object):
	dp = {0:[],1:[TreeNode(0)]}
	def allPossibleFBT(self, n):
	if n in Solution.dp:
	return Solution.dp[n]
	ans = []
	for i in range(n):
	j = n-1-i
	for l in self.allPossibleFBT(i):
	for r in self.allPossibleFBT(j):
	bns = TreeNode(0)
	bns.left = l
	bns.right = r
	ans.append(bns)
	Solution.dp[n]=ans
	return ans

view raw all-possible-full-binary-trees.py hosted with ❤ by GitHub