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POJ 3087 Shuffle'm Up （模拟）

2024-07-17 23:12:32   223人阅读

Shuffle‘m Up
Time Limit: 1000MS Memory Limit: 65536K
Total Submissions: 5850 Accepted: 2744

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 S1and 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

Source

Greater New York 2006
一道模拟题，
解题思路：这个直接模拟（或者退化的BFS或DFS吧，就一种情况，汗。~）题目所要求的Shuffle的过程就行了，只是要注意搜索失败的条件。当S1和S2又回到初始化状态时就是搜索失败的条件，为什么会这样呢？把所有的情况放在一个集合里面，Shuffle会模拟到所有情况，直到回到初始状态，无限循环下去。
代码：
#include <iostream>
#include <algorithm>
#include <cstdio>
#include <cstring>
#include <cmath>
using namespace std;
#define M 110
char mat[220],S1[M],S2[M];
char map[1000][220];
int main()
{
  int n,m,i,j,x,k;
  while(scanf("%d",&m)!=EOF&&m)
  {
      for(k=1;k<=m;k++)
      {
          memset(map,‘0‘,sizeof(map));
          memset(mat,‘0‘,sizeof(mat));
          scanf("%d%s%s%s",&n,S1,S2,mat);
          x=1;
          while(1)
          {
             for(i=0;i<n;i++)
             {
                 map[x][2*i]=S2[i];  //S2放下面。
                 map[x][2*i+1]=S1[i]; //S1放上面。
             }
            map[x][2*n]=NULL;          //要截断，不然根本匹配不上。
            if(strcmp(map[x],mat)==0)
            break;
            for(i=0;i<x;i++)
            if(strcmp(map[i],map[x])==0)
            {x=-1;break;}     //这个break没跳出while只是跳出for循环。
            for(i=0;i<=n-1;i++)
            S1[i]=map[x][i];
            for(i=n;i<2*n;i++)
            S2[i-n]=map[x][i];
            if(x==-1) break; 
            x++;
          }
          printf("%d %d\n",k,x);
   }
  }
  return 0;
}


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