算法题/重建二叉树

输入某二叉树的前序遍历和中序遍历的结果，请重建出该二叉树。假设输入的前序遍历和中序遍历的结果中都不含重复的数字。例如输入前序遍历序列{1,2,4,7,3,5,6,8}和中序遍历序列{4,7,2,1,5,3,8,6}，则重建二叉树并返回。

#coding:utf-8
class TreeNode:
def __init__(self, x):
self.val = x
self.left = None
self.right = None

class Solution:
def reConstructBinaryTree(self, pre, tin):
# write code here
if len(pre) == 0:
return None
elif len(pre) == 1:
return TreeNode(pre[0])
else:
ans = TreeNode(pre[0])
ans.left = self.reConstructBinaryTree(pre[1:tin.index(pre[0])+1], tin[:tin.index(pre[0])])
ans.right = self.reConstructBinaryTree(pre[tin.index(pre[0])+1:], tin[tin.index(pre[0])+1:])
return ans

if __name__ == '__main__':
s = Solution()
#根节点
print(s.reConstructBinaryTree([1,2,4,7,3,5,6,8],[4,7,2,1,5,3,8,6]).left.val)