POJ 3111 K Best

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

const int MAXN=100005;
const double eps=1e-6;
double a[MAXN],b[MAXN],d[MAXN];
int N,K;

bool cmp1(double x,double y){
    return x>y;
}

bool calc(double r){
    for(int i=0;i<N;i++)
        d[i]=a[i]-b[i]*r;
    double sum=0;
    sort(d,d+N,cmp1);
    for(int i=0;i<K;i++)
        sum+=d[i];
    return sum<=0.0;
}

struct Node{
    int id;
    double d;
}node[MAXN];

bool cmp2(Node x,Node y){
   return x.d>y.d;
}

bool cmp3(Node x,Node y){
    return x.id<y.id;
}

int main(){
    cin>>N>>K;
    for(int i=0;i<N;i++)
        scanf("%lf%lf",&a[i],&b[i]);

    double l=0.0,r=100000000.0;
    while(r-l>eps){  //这儿的精度要求有点高
        double mid=(l+r)/2.0;
        if(calc(mid))
            r=mid;
        else
            l=mid;
    }
    for(int i=0;i<N;i++){
        node[i].id=i+1;
        node[i].d=a[i]-l*b[i];
    }

    sort(node,node+N,cmp2);
    for(int i=0;i<K;i++)
        printf("%d%c",node[i].id,i+1==K?‘\n‘:‘ ‘);
    return 0;
}