POJ2976 Dropping tests 01分数规划

二分答案ans，可让精度恶心死我了

找到使a[i]-l*b[i]最大的l。

#include<iostream>
#include<cstdio>
#include<algorithm>
using namespace std;

const double eps = 1e-7;

int n,k;
double ans,a[1010],b[1010],d[1010];

int main(){
    while(true){
        cin >> n >> k;
        if(n == 0&&k == 0)break;
        for(int i = 1;i <= n;i++)scanf("%lf",&a[i]);
        for(int i = 1;i <= n;i++)scanf("%lf",&b[i]);
        double l = 0.0,r = 1.0,mid;
        for(int i = 1;i <= 300;i++){
            mid = (l+r)/2;
            for(int i = 1;i <= n;i++)d[i] = a[i]-mid*b[i];
            sort(d+1,d+n+1); 
            double sum = 0.0;
            for(int i = k+1;i <= n;i++)sum += d[i];
            if(sum >= -eps)ans = mid,l = mid;
            else r = mid;
        }
        printf("%.0f
",ans*100);
    }    
return 0;
}