提高水平

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https://nanti.jisuanke.com/t/31436

状压dp。

#include<cstdio>
#include<cctype>
#include<algorithm>
inline int getint() {
    register char ch;
    while(!isdigit(ch=getchar()));
    register int x=ch^'0';
    while(isdigit(ch=getchar())) x=(((x<<2)+x)<<1)+(ch^'0');
    return x;
}
const int N=20;
int a[N][N],f[1<<N],w[N][1<<N];
inline int lowbit(const int &x) {
    return x&-x;
}
inline int lg2(const float &x) {
    return ((unsigned&)x>>23&255)-127;
}
int main() {
    freopen("proficiency.in","r",stdin);
    freopen("proficiency.out","w",stdout);
    const int n=getint(),all=(1<<n)-1;
    for(register int i=0;i<n;i++) {
        for(register int j=0;j<n;j++) {
            a[i][j]=getint();
        }
    }
    for(register int i=0;i<n;i++) {
        for(register int j=1;j<=all;j++) {
            w[i][j]=w[i][j^lowbit(j)]+a[lg2(lowbit(j))][i];
        }
    }
    for(register int i=1;i<=all;i++) {
        for(register int j=0;j<n;j++) {
            if((i>>j)&1) {
                f[i]=std::max(f[i],f[i^(1<<j)]+w[j][i]);
            }
        }
    }
    printf("%d\n",f[all]);
    return 0;
}