九度Online Judge

OJ新增积分机制,如有任何问题或者建议,请发帖到九度论坛OJ意见反馈版,祝大家一切顺利!
亲,九度OJ官方微博开通了,欢迎你来粉!微博地址:weibo.com/jobdu

 题目1044-九度Online Judge,用代码记录你的成长之路!

题目1044:Pre-Post

时间限制:1 秒

内存限制:32 兆

特殊判题:

提交:967

解决:548

题目描述:

        We are all familiar with pre-order, in-order and post-order traversals of binary trees. A common problem in data structure classes is to find the pre-order traversal of a binary tree when given the in-order and post-order traversals. Alternatively, you can find the post-order traversal when given the in-order and pre-order. However, in general you cannot determine the in-order traversal of a tree when given its pre-order and post-order traversals. Consider the four binary trees below:



    All of these trees have the same pre-order and post-order traversals. This phenomenon is not restricted to binary trees, but holds for general m-ary trees as well.

输入:

        Input will consist of multiple problem instances. Each instance will consist of a line of the form
m s1 s2
        indicating that the trees are m-ary trees, s1 is the pre-order traversal and s2 is the post-order traversal.All traversal strings will consist of lowercase alphabetic characters. For all input instances, 1 <= m <= 20 and the length of s1 and s2 will be between 1 and 26 inclusive. If the length of s1 is k (which is the same as the length of s2, of course), the first k letters of the alphabet will be used in the strings. An input line of 0 will terminate the input.

输出:
        For each problem instance, you should output one line containing the number of possible trees which would result in the pre-order and post-order traversals for the instance. All output values will be within the range of a 32-bit signed integer. For each problem instance, you are guaranteed that there is at least one tree with the given pre-order and post-order traversals.

样例输入:
2 abc cba
2 abc bca
10 abc bca
13 abejkcfghid jkebfghicda
样例输出:
4
1
45
207352860
来源:
2008年上海交通大学计算机研究生机试真题
答疑:
解题遇到问题?分享解题心得?讨论本题请访问:http://t.jobdu.com/thread-7768-1-1.html