bzoj5090[lydsy11月赛]组题

裸的01分数规划,二分答案,没了.

#include<cstdio>
#include<algorithm>
using namespace std;
const int maxn=100005;
int a[maxn];
double b[maxn];
double c[maxn];
typedef long long ll;
ll gcd(ll a,ll b){return (b==0)?a:gcd(b,a%b);
}
int main(){int n,k;scanf("%d%d",&n,&k);for(int i=1;i<=n;++i)scanf("%d",a+i);double l=-1e8,r=1e8;int R=0;while(r-l>1e-5){double mid=(l+r)/2.0;for(int i=1;i<=n;++i)b[i]=a[i]-mid;for(int i=1;i<=n;++i)b[i]+=b[i-1];c[0]=0;for(int i=1;i<=n;++i){c[i]=min(c[i-1],b[i]);}bool flag=false;for(int i=k;i<=n;++i){if(c[i-k]<=b[i]){flag=true;R=i;break;}}if(flag)l=mid;else r=mid;}double Min=0;int L=0;for(int j=1;j<=R-k;++j){if(b[j]<Min)L=j,Min=b[j];}ll sum=0;for(int i=L+1;i<=R;++i)sum+=a[i];if(sum<0){printf("-");sum=-sum;}ll g=gcd(sum,R-L);printf("%lld/%lld\n",sum/g,(R-L)/g);return 0;
}