1 #include<cstdio> 2 #include<cctype> 3 using namespace std ; 4 5 struct state { 6 int len ; 7 int p ; 8 int h ; 9 int last ; 10 state ( const int len , const int p , const int h , 11 const int last ) : len ( len ) , p ( p ) , h ( h ) , 12 last ( last ) {} ; 13 int hash () const { 14 return len * 6000 + 250 * p + h * 7 + last ; 15 //this is a perfect hash 16 } 17 } ; 18 19 const int MAXN = 25 ; 20 const long long MOD = ( long long ) ( 1e9 + 7 ) ; 21 int N , M , K ; 22 23 int G [ MAXN ] [ MAXN ] ; 24 char s [ MAXN ] ; 25 26 const int size_of_dp = 2000000 ; 27 long long dp [ size_of_dp ] ; 28 bool vis [ size_of_dp ] ; 29 30 int main () ; //complete checking checked 31 long long D ( const state o ) ; //complete 32 long long T ( const state o , const int p ) ;//complete 33 long long T0 ( const state o , const int p ) ;//complete 34 long long T1 ( const state o , const int p ) ;//complete 35 long long T2 ( const state o , const int p ) ;//complete 36 long long T3 ( const state o , const int p ) ;//complete 37 long long T4 ( const state o , const int p ) ;//complete 38 long long T5 ( const state o , const int p ) ;//complete 39 40 long long D ( const state o ) { 41 if ( vis [ o . hash () ] ) return dp [ o . hash () ] ; 42 vis [ o . hash () ] = true ; 43 if ( o . len == K ) { 44 if ( o . h == 0 && o . last < 3 ) 45 return dp [ o . hash () ] = 1 ; 46 else return 0 ; 47 } 48 long long ans = 0 ; 49 for ( int i = 1 ; i <= N ; ++ i ) 50 if ( G [ o . p ] [ i ] ) { 51 ans += T ( o , i ) ; 52 ans %= MOD ; 53 } 54 #ifdef DEBUG 55 printf ( "(%d,%d,%d,%d)=%lld " , o . len , o . p , o . h , o . last , ans ) ; 56 #endif 57 return dp [ o . hash () ] = ans ; 58 } 59 60 long long T ( const state o , const int p ) { 61 switch ( o . last ) { 62 case 0 : return T0 ( o , p ) ; 63 case 1 : return T1 ( o , p ) ; 64 case 2 : return T2 ( o , p ) ; 65 case 3 : return T3 ( o , p ) ; 66 case 4 : return T4 ( o , p ) ; 67 case 5 : return T5 ( o , p ) ; 68 } 69 return 233 ; 70 } 71 72 int main () { 73 freopen ( "trace.in" , "r" , stdin ) ; 74 freopen ( "trace.out" , "w" , stdout ) ; 75 scanf ( "%d%d%d" , & N , & M , & K ) ; 76 scanf ( "%s" , s + 1 ) ; 77 while ( M -- ) { 78 int a , b ; 79 scanf ( "%d%d" , & a , & b ) ; 80 G [ a ] [ b ] = G [ b ] [ a ] = 1 ; 81 } 82 for ( int i = 1 ; i <= N ; ++ i ) G [ 0 ] [ i ] = 1 ; 83 printf ( "%lld " , D ( state ( 0 , 0 , 0 , 3 ) ) ) ; 84 return 0 ; 85 } 86 87 long long T0 ( const state o , const int p ) { 88 if ( s [ p ] == ')' && o . h > 0 ) 89 return D ( state ( o . len + 1 , p , o . h - 1 , 2 ) ) ; 90 if ( s [ p ] == '+' || s [ p ] == '-' || 91 s [ p ] == '*' || s [ p ] == '/' ) 92 return D ( state ( o . len + 1 , p , o . h , 5 ) ) ; 93 return 0 ; 94 } 95 96 long long T1 ( const state o , const int p ) { 97 if ( isdigit ( s [ p ] ) ) 98 return D ( state ( o . len + 1 , p , o . h , 1 ) ) ; 99 if ( s [ p ] == '+' || s [ p ] == '-' || 100 s [ p ] == '*' || s [ p ] == '/' ) 101 return D ( state ( o . len + 1 , p , o . h , 5 ) ) ; 102 if ( s [ p ] == ')' && o . h > 0 ) 103 return D ( state ( o . len + 1 , p , o . h - 1 , 2 ) ) ; 104 return 0 ; 105 } 106 107 long long T2 ( const state o , const int p ) { 108 if ( s [ p ] == '+' || s [ p ] == '-' || 109 s [ p ] == '*' || s [ p ] == '/' ) 110 return D ( state ( o . len + 1 , p , o . h , 5 ) ) ; 111 if ( s [ p ] == ')' && o . h > 0 ) 112 return D ( state ( o . len + 1 , p , o . h - 1 , 2 ) ) ; 113 return 0 ; 114 } 115 116 long long T3 ( const state o , const int p ) { 117 if ( s [ p ] == '(' ) 118 return D ( state ( o . len + 1 , p , o . h + 1 , 3 ) ) ; 119 if ( s [ p ] == '-' ) 120 return D ( state ( o . len + 1 , p , o . h , 4 ) ) ; 121 if ( s [ p ] == '0' ) 122 return D ( state ( o . len + 1 , p , o . h , 0 ) ) ; 123 if ( s [ p ] >= '1' && s [ p ] <= '9' ) 124 return D ( state ( o . len + 1 , p , o . h , 1 ) ) ; 125 return 0 ; 126 } 127 128 long long T4 ( const state o , const int p ) { 129 if ( s [ p ] == '0' ) 130 return D ( state ( o . len + 1 , p , o . h , 0 ) ) ; 131 if ( s [ p ] >= '1' && s [ p ] <= '9' ) 132 return D ( state ( o . len + 1 , p , o . h , 1 ) ) ; 133 if ( s [ p ] == '(' ) 134 return D ( state ( o . len + 1 , p , o . h + 1 , 3 ) ) ; 135 return 0 ; 136 } 137 138 long long T5 ( const state o , const int p ) { 139 if ( s [ p ] == '0' ) 140 return D ( state ( o . len + 1 , p , o . h , 0 ) ) ; 141 if ( s [ p ] >= '1' && s [ p ] <= '9' ) 142 return D ( state ( o . len + 1 , p , o . h , 1 ) ) ; 143 if ( s [ p ] == '(' ) 144 return D ( state ( o . len + 1 , p , o . h + 1 , 3 ) ) ; 145 return 0 ; 146 }
今天Z老把BJOI的题当练习给我们做，结果这道题只有50分。检查出来多写了一个+1，一脸。。