bzoj1231: [Usaco2008 Nov]mixup2 混乱的奶牛

简单的状压，直接暴力n^2枚举就好了。

#include<cstdio>#include<algorithm>#include<cstring>#define fo(i,a,b) for(int i=a;i<=b;i++)#define fd(i,a,b) for(int i=a;i>=b;i--)using namespace std;const int N=1e5+5;const int M=17;int n,m,tot,a[N];typedef long long ll;ll f[M][1<<16],ans;int main(){    scanf("%d%d",&n,&m);    tot=(1<<n)-1;    fo(i,1,n)scanf("%d",&a[i]);    fo(i,1,n)f[i][1<<(i-1)]=1;    fo(i,0,tot)    fo(j,1,n)    if (i&(1<<(j-1)))    fo(k,1,n)    if ((i|(1<<(k-1)))!=i&&abs(a[j]-a[k])>m)    f[k][i|(1<<(k-1))]+=f[j][i];    fo(i,1,n)ans+=f[i][tot];    printf("%lld\n",ans);}