POJ 3087 Shuffle'm Up（模拟）

题目链接：http://poj.org/problem?id=3087

Shuffle’m Up
Time Limit: 1000MS Memory Limit: 65536K
Total Submissions: 10756 Accepted: 4971
Description

A common pastime for poker players at a poker table is to shuffle stacks of chips. Shuffling chips is performed by starting with two stacks of poker chips, S1 and S2, each stack containing C chips. Each stack may contain chips of several different colors.

The actual shuffle operation is performed by interleaving a chip from S1 with a chip from S2 as shown below for C = 5:

The single resultant stack, S12, contains 2 * C chips. The bottommost chip of S12 is the bottommost chip from S2. On top of that chip, is the bottommost chip from S1. The interleaving process continues taking the 2nd chip from the bottom of S2 and placing that on S12, followed by the 2nd chip from the bottom of S1 and so on until the topmost chip from S1 is placed on top of S12.

After the shuffle operation, S12 is split into 2 new stacks by taking the bottommost C chips from S12 to form a new S1 and the topmost C chips from S12 to form a new S2. The shuffle operation may then be repeated to form a new S12.

For this problem, you will write a program to determine if a particular resultant stack S12 can be formed by shuffling two stacks some number of times.

Input

The first line of input contains a single integer N, (1 ≤ N ≤ 1000) which is the number of datasets that follow.

Each dataset consists of four lines of input. The first line of a dataset specifies an integer C, (1 ≤ C ≤ 100) which is the number of chips in each initial stack (S1 and S2). The second line of each dataset specifies the colors of each of the C chips in stack S1, starting with the bottommost chip. The third line of each dataset specifies the colors of each of the C chips in stack S2 starting with the bottommost chip. Colors are expressed as a single uppercase letter (A through H). There are no blanks or separators between the chip colors. The fourth line of each dataset contains 2 * C uppercase letters (A through H), representing the colors of the desired result of the shuffling of S1 and S2 zero or more times. The bottommost chip’s color is specified first.

Output

Output for each dataset consists of a single line that displays the dataset number (1 though N), a space, and an integer value which is the minimum number of shuffle operations required to get the desired resultant stack. If the desired result can not be reached using the input for the dataset, display the value negative 1 (−1) for the number of shuffle operations.

Sample Input

2
4
AHAH
HAHA
HHAAAAHH
3
CDE
CDE
EEDDCC
Sample Output

1 2
2 -1

【中文题意】给你s1,s2,s12,问你是否经过操作能将s1和s2组成成s12，如果可以的话，输出次数，否则输出-1，输出的第一个整数代表第几组，第二个整数是次数。给出的s1，s2,s3是从下到上的字符串，操作的方法为：
将s1和s2交叉放置组成ss，然后新的s1为ss的从下到上的前一半，s2位ss从下到上的后一半。问你ss==s12的时候经过了几次操作，或者不可能ss==s12的话输出-1 。
【思路分析】按照给的要求依次操作，每次操作完之后记录ss，假如操作到某一次的时候ss已经在之前出现过，那么此时操作成了一个环，是不可能构成s12的，输出-1 。
【AC代码】

#include<cstdio>#include<cstring>#include<cmath>#include<iostream>#include<map>#include<queue>#include<string>#include<algorithm>using namespace std;string s1,s2,ss,s12;int main(){    int t,iCase=0,n;    scanf("%d",&t);    while(t--)    {        scanf("%d",&n);        cin>>s1;        cin>>s2;        cin>>s12;        map<string ,int>m;        int step=0,flag=0;        while(1)        {            ss="";            for(int i=0; i<n; i++)            {                ss+=s2[i];                ss+=s1[i];            }            step++;            if(ss==s12)            {                flag=1;                break;            }            else            {                if(m[ss]==1)                    break;                else                    m[ss]++;            }            s1=ss.substr(0,n);            s2=ss.substr(n,n);        }        if(flag)        {            printf("%d %d\n",++iCase,step);        }        else        {            printf("%d ",++iCase);            printf("-1\n");        }    }    return 0;}