POJ 3450 Corporate Identity

二分枚举+KMP

之前没注意字典序最小，WA了N次……

  1 #include <cstdio>

  2 #include <cstring>

  3 #include <cstdlib>

  4 #include <algorithm>

  5 

  6 using namespace std;

  7 

  8 const int MAXN = 4010;

  9 const int MAXL = 210;

 10 

 11 int N;

 12 char str[MAXN][MAXL];

 13 char temp[MAXL];

 14 char anser[MAXL];

 15 int nextval[MAXL];

 16 int len[MAXN];

 17 

 18 void GetNextVal( char *s, int lenth )

 19 {

 20     int i = 0, j = -1;

 21     nextval[0] = -1;

 22     while ( i < lenth )

 23     {

 24         if ( j == -1 || s[i] == s[j] )

 25         {

 26             ++i, ++j;

 27             if ( s[i] != s[j] ) nextval[i] = j;

 28             else nextval[i] = nextval[j];

 29         }

 30         else j = nextval[j];

 31     }

 32     return;

 33 }

 34 

 35 bool KMP( char *t, char *s, int lenth, int lenn )

 36 {

 37     GetNextVal( t, lenth );

 38     int i = 0, j = 0;

 39     while ( j < lenn )

 40     {

 41         if ( i == -1 || s[j] == t[i] )

 42         {

 43             ++i, ++j;

 44             if ( i == lenth ) return true;

 45         }

 46         else i = nextval[i];

 47         //if ( i == lenth ) return true;

 48     }

 49     return false;

 50 }

 51 

 52 bool check( int tpL )

 53 {

 54     bool flag = false;

 55     bool ok = false;

 56     for ( int st = 0; st + tpL - 1 < len[0]; ++st )

 57     {

 58         for ( int k = 0; k < tpL; ++k )

 59             temp[k] = str[0][ st + k ];

 60         temp[ tpL ] = '\0';

 61         //puts(temp);

 62 

 63         ok = true;

 64         for ( int i = 1; i < N; ++i )

 65             if ( !KMP( temp, str[i], tpL, len[i] ) )

 66             {

 67                 ok = false;

 68                 break;

 69             }

 70         if ( ok )

 71         {

 72             flag = true;

 73             if ( anser[0] == '\0' ||

 74                 ( strlen(anser) == strlen(temp) && strcmp( anser, temp ) > 0 ) || ( strlen(anser) < strlen(temp) ) )

 75                 strcpy( anser, temp );

 76         }

 77     }

 78     return flag;

 79 }

 80 

 81 int main()

 82 {

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

 84     {

 85         int bound = 1 << 30;

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

 87         {

 88             scanf( "%s", str[i] );

 89             len[i] = strlen( str[i] );

 90             bound = min( bound, len[i] );

 91         }

 92 

 93         int low = 0;

 94         int high = bound;

 95         int mid, ans = 0;

 96         anser[0] = '\0';

 97         while ( low <= high )

 98         {

 99             mid = ( low + high ) >> 1;

100             if ( check( mid ) )

101             {

102                 ans = mid;

103                 low = mid + 1;

104             }

105             else high = mid - 1;

106         }

107 

108         if ( !ans ) puts("IDENTITY LOST");

109         else puts(anser);

110     }

111     return 0;

112 }