2019年3月20日 894. All Possible Full Binary Trees

实际上感觉是带参的宽搜，但是因为懒得写。。还是强行写了深搜。

这道题在lt上提交有bug，好像是因为我用了node的未声明变量？单独测试是没问题的

class Solution(object):
    
    result = []
    
    def buildNode(self, v, father, root):
        ret = TreeNode(v)
        ret.father = father
        ret.root = root
        return ret
   
    def possibleFBT(self, n, node):
        
        if n == 0:
            self.result.append(copy.deepcopy(node.root))
            return
        
        node.left = self.buildNode(0, node, node.root)
        node.right = self.buildNode(0, node, node.root)
        self.possibleFBT(n-2, node.left)
        if n-2 > 0:
            self.possibleFBT(n-2, node.right)
        
        if node.father and n-2 > 0 and node.father.right != node:
            self.possibleFBT(n-2, node.father.right)
        
        node.left = None
        node.right = None
    
    def allPossibleFBT(self, N):
        """
        :type N: int
        :rtype: List[TreeNode]
        """
        if N % 2 == 0:
            return []
        root = self.buildNode(0, None, None)
        root.root = root
        self.possibleFBT(N-1, root)
        return self.result