这题真的卡精度，耗了一个下午，感谢lyd，顺便提供ac代码，以便后人

#include <iostream>
#include <cstdio>
#include <algorithm>
#define il inline
#define ri register
#define db double
#define exact 0.00000001
int n,k;db a[2001],b[2001],c[2001];
using namespace std;
il bool check(db);
il db dfs(db,db);
int main(){
    int i,j;
    while(scanf("%d%d",&n,&k),n||k){
        for(i=1;i<=n;++i)scanf("%lf",&a[i]);
        for(i=1;i<=n;++i)scanf("%lf",&b[i]);
        printf("%0.f\n",dfs(0,1));
    }
    return 0;
}
il bool check(db s){
    int i;db j(0);
    for(i=1;i<=n;++i)c[i]=a[i]-s*b[i];
    sort(c+1,c+n+1);for(i=k+1;i<=n;++i)j+=c[i];
    if(j>exact)return true;return false;
}
il db dfs(db l,db r){
    db mid;
    while(r-l>exact){
        mid=(l+r)/2;
        if(check(mid))l=mid+exact;
        else r=mid-exact;
    }return (l+r)*50;
}

• Re:提供ac代码 (1728) a1b3c7d9 2019-05-01 17:34:11