题目链接

wyh的物品

题目思路

01分数规划入手题，千万不要把value和weight看反！

代码实现

#include<bits/stdc++.h>
using namespace std;
#define ll long long
const int Max=1e5+5;
int a[Max],b[Max];
int n,k;
double p[Max];
bool cmp(double aaa,double bbb)
{
    return aaa>bbb;
}
bool check(double x)
{
    double res=0;
    for(int i=1;i<=n;i++)
        p[i]=b[i]-x*a[i];
    sort(p+1,p+1+n,cmp);
    for(int i=1;i<=k;i++)
        res+=p[i];
    return res>=0;
}
int main()
{
    int t;
    cin>>t;
    while(t--)
    {
        cin>>n>>k;
        for(int i=1;i<=n;i++)
            cin>>a[i]>>b[i];
        double l=0,r=1e9;
        double ans;
        while(r-l>=1e-6)
        {
            double mid=(l+r)/2;
            if(check(mid))
            {
                ans=l;
                l=mid;
            }
            else r=mid;
        }
        cout<<fixed<<setprecision(2)<<ans<<endl;
    }
    return 0;
}