【题解】P1171 售货员的难题

Tags

搜索，状压​。

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裸的旅行商问题

#include <stdio.h>
#include <string.h>
#define re register
#define GC getchar()
#define Clean(X,K) memset(X,K,sizeof(X))
#define U unsigned
#define Min(X,Y) (X<Y?X:Y)
short Qread () {
    short X =  ;
    char C = GC ;
    while (C > '' || C < '') C = GC ;
    while (C >='' && C <='') {
        X = X *  + C - '' ;
        C = GC ;
    }
    return X ;
}
const short Maxn =  , INF = ( << ) - ;
U short int A[Maxn][Maxn] , N ;
short F[Maxn][ << Maxn];
void DFS (short Now , U X) {
    if (F[Now][X] != -) return ;
    F[Now][X] = INF;
    for (re int i =  ; i < N; ++ i) {
        if ((X & ( << i)) && Now != i) {
            DFS (i , X & (~ ( << Now))) ;
            F[Now][X] = Min (F[Now][X] , A[i][Now] + F[i][X & (~ ( << Now))]) ;
        }
    }
}
int main () {
    //freopen ("P1171.in" , "r" , stdin) ;
    N = Qread () ;
    for (re int i =  ; i < N; ++ i) for (re int j =  ; j < N; ++ j) A[i][j] = Qread () ;
    Clean (F , -) ;
    F[][] =  ;
    for (re int i =  ; i < N; ++ i) DFS (i , ( << N) - ) ;
    int Ans = INF ;
    for (re int i =  ; i < N; ++ i) Ans = Min (Ans ,A[i][] + F[i][( << N) - ]) ;
    printf ("%d\n" , Ans) ;
    fclose (stdin) , fclose (stdout) ;
    return  ;
}