题目：http://www.lydsy.com/JudgeOnline/problem.php?id=1079
囧囧的一道六维DP，记得用long long
代码：
#include
#include
#include
#include
#include
using namespace std ;
#define MOD( x ) ( x %= MAX )
#define MAX 1000000007
#define ll long long
bool f[ 16 ][ 16 ][ 16 ][ 16 ][ 16 ][ 16 ] ;
ll dp[ 16 ][ 16 ][ 16 ][ 16 ][ 16 ][ 16 ] , k ;
struct state {
int a , b , c , d , e , x ;
state( ) {
a = b = c = d = e = x = 0 ;
}
state( int _a , int _b , int _c , int _d , int _e , int _x ) : a( _a ) , b( _b ) , c( _c ) , d( _d ) , e( _e ) , x( _x ) {
}
} ;
queue < state > Q ;
void Init( ) {
memset( f , false , sizeof( f ) ) ;
memset( dp , 0 , sizeof( dp ) ) ;
state S ;
cin >> k ;
for ( int i = 0 ; i ++ < k ; ) {
int x ; cin >> x ;
switch ( x ) {
case 1 :
S.a ++ ;
break ;
case 2 :
S.b ++ ;
break ;
case 3 :
S.c ++ ;
break ;
case 4 :
S.d ++ ;
break ;
case 5 :
S.e ++ ;
break ;
}
}
while ( ! Q.empty( ) ) Q.pop( ) ;
int a = S.a , b = S.b , c = S.c , d = S.d , e = S.e , x = S.x ;
if ( a ) {
f[ a - 1 ][ b ][ c ][ d ][ e ][ 0 ] = true ;
dp[ a - 1 ][ b ][ c ][ d ][ e ][ 0 ] = a ;
Q.push( state( a - 1 , b , c , d , e , 0 ) ) ;
}
if ( b ) {
f[ a + 1 ][ b - 1 ][ c ][ d ][ e ][ 1 ] = true ;
dp[ a + 1 ][ b - 1 ][ c ][ d ][ e ][ 1 ] = b ;
Q.push( state( a + 1 , b - 1 , c , d , e , 1 ) ) ;
}
if ( c ) {
f[ a ][ b + 1 ][ c - 1 ][ d ][ e ][ 2 ] = true ;
dp[ a ][ b + 1 ][ c - 1 ][ d ][ e ][ 2 ] = c ;
Q.push( state( a , b + 1 , c - 1 , d , e , 2 ) ) ;
}
if ( d ) {
f[ a ][ b ][ c + 1 ][ d - 1 ][ e ][ 3 ] = true ;
dp[ a ][ b ][ c + 1 ][ d - 1 ][ e ][ 3 ] = d ;
Q.push( state( a , b , c + 1 , d - 1 , e , 3 ) ) ;
}
if ( e ) {
f[ a ][ b ][ c ][ d + 1 ][ e - 1 ][ 4 ] = true ;
dp[ a ][ b ][ c ][ d + 1 ][ e - 1 ][ 4 ] = e ;
Q.push( state( a , b , c , d + 1 , e - 1 , 4 ) ) ;
}
}
void Update( int a , int b , int c , int d , int e , int x , ll cnt ) {
if ( ! f[ a ][ b ][ c ][ d ][ e ][ x ] ) {
f[ a ][ b ][ c ][ d ][ e ][ x ] = true ;
Q.push( state( a , b , c , d , e , x ) ) ;
}
dp[ a ][ b ][ c ][ d ][ e ][ x ] += cnt ;
MOD( dp[ a ][ b ][ c ][ d ][ e ][ x ] ) ;
}
void Solve( ) {
while ( ! Q.empty( ) ) {
state v = Q.front( ) ; Q.pop( ) ;
int a = v.a , b = v.b , c = v.c , d = v.d , e = v.e , x = v.x ;
ll temp = dp[ a ][ b ][ c ][ d ][ e ][ x ] ;
if ( a ) {
ll rec = a - ( x == 1 ) ;
Update( a - 1 , b , c , d , e , 0 , temp * rec ) ;
}
if ( b ) {
ll rec = b - ( x == 2 ) ;
Update( a + 1 , b - 1 , c , d , e , 1 , temp * rec ) ;
}
if ( c ) {
ll rec = c - ( x == 3 ) ;
Update( a , b + 1 , c - 1 , d , e , 2 , temp * rec ) ;
}
if ( d ) {
ll rec = d - ( x == 4 ) ;
Update( a , b , c + 1 , d - 1 , e , 3 , temp * rec ) ;
}
if ( e ) {
ll rec = e ;
Update( a , b , c , d + 1 , e - 1 , 4 , temp * rec ) ;
}
}
cout << dp[ 0 ][ 0 ][ 0 ][ 0 ][ 0 ][ 0 ] << endl ;
}
int main( ) {
Init( ) ;
Solve( ) ;
return 0 ;
}