def recursion(self, root, left, right, inorderDict, preorder):
# step 1 : 判定 是否 到达 叶子节点
if left > right:
return
# step 2 : 构建根节点
node = Tree(preorder[root])
# step 3 : 搜索 根节点 在 中序遍历 中 的位置
index = inorderDict[preorder[root]]
# step 4 : 分割 左右子树
node.left = self.recursion(root + 1, left, index - 1, inorderDict,
preorder)
node.right = self.recursion(index - left + root + 1, index + 1, right,
inorderDict, preorder)
return node
def left_right(left, right):
if left > right:
return [None]
if (left, right) in dct:
return dct[(left, right)]
ret = []
for i in range(left, right + 1):
left_lst = left_right(left, i - 1)
right_lst = left_right(i + 1, right)
for L in left_lst:
for R in right_lst:
app_Tree = Tree(i)
app_Tree.left = L
app_Tree.right = R
ret.append(app_Tree)
dct[(left, right)] = ret
return ret