UVa 141 - The Spot Game

题目链接：http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=111&page=show_problem&problem=77

题意：判断摆放过程中是否出现已经出现过的图案，图案可以顺时针旋转90°，180°和水平翻转。

分析：字符串哈希判重

  1 #include <cstdio>

  2 #include <cstring>

  3 

  4 const int MAXN = 100007;

  5 

  6 char map[52][52];

  7 char temp[52][52];

  8 char temp2[52][52];

  9 bool vis[MAXN];

 10 int N;

 11 

 12 //void show( char (*str)[52] )

 13 //{

 14 //    for ( int i = 0; i < N; ++i )

 15 //    {

 16 //        for ( int j = 0; j < N; ++j )

 17 //        putchar(str[i][j]);

 18 //        puts("");

 19 //    }

 20 //}

 21 

 22 unsigned int BKDRHash( char (*str)[52] )

 23 {

 24     unsigned int seed = 31;

 25     unsigned int hash = 0;

 26 

 27     for ( int i = 0; i < N; ++i )

 28       for ( int j = 0; j < N; ++j )

 29          hash = hash * seed + str[i][j];

 30 

 31     return (hash & 0x7FFFFFFF) % MAXN;

 32 }

 33 

 34 void Rotate( char (*str)[52], char (*ttemp)[52] )

 35 {

 36     for ( int i = 0; i < N; ++i )

 37       for ( int j = 0; j < N; ++j )

 38          ttemp[ j ][ N - 1 - i ] = str[i][j];

 39    // show(str);

 40    // show(ttemp);

 41    // puts("-------------");

 42     int hash = BKDRHash( ttemp );

 43    // printf("%d\n", hash);

 44     vis[hash] = true;

 45     return;

 46 }

 47 

 48 void Reflact( char (*str)[52] )

 49 {

 50     for ( int i = 0; i < N; ++i )

 51       for ( int j = 0; j < N; ++j )

 52          temp[i][N - 1 - j] = str[i][j];

 53 

 54     int hash = BKDRHash( temp );

 55     vis[hash] = true;

 56     return;

 57 }

 58 

 59 int main()

 60 {

 61     int x, y;

 62     char ch[3];

 63     int where, who;

 64     while ( scanf( "%d", &N ), N )

 65     {

 66         bool flag = false;

 67         memset( vis, false, sizeof(vis) );

 68         memset( map, '.', sizeof(map) );

 69 

 70         for ( int i = 0; i < N * 2; ++i )

 71         {

 72             scanf("%d%d%s", &x, &y, ch);

 73             if ( !flag )

 74             {

 75                 switch( ch[0] )

 76                 {

 77                 case '+':

 78                     map[x - 1][y - 1] = '#';

 79                     break;

 80 

 81                 case '-':

 82                     map[x - 1][y - 1] = '.';

 83                     break;

 84                 }

 85                 int hash = BKDRHash( map );

 86      //           printf("%d\n", hash);

 87                 if ( vis[hash] )

 88                 {

 89                     flag = true;

 90                     where = i + 1;

 91                     if ( i % 2 ) who = 1;

 92                     else who = 2;

 93                 }

 94                 vis[hash] = true;

 95                 Rotate( map, temp );

 96                 Rotate( temp, temp2 );

 97                 Reflact( map );

 98             }

 99         }

100         if ( !flag ) puts("Draw");

101         else printf( "Player %d wins on move %d\n", who, where );

102     }

103     return 0;

104 }