答题记录

#include<bits/stdc++.h> 
using namespace std;
struct pp{
	int x,y;
};
pp a[101];
bool cmp(pp x,pp y){
	return x.x*y.y<x.y*y.x;
}
int main(){
    int n,b;
	double sum=0;
	cin>>n>>b;
	for(int i=0;i<n;i++){
		cin>>a[i].x>>a[i].y;
	}
	sort(a,a+n,cmp);
	for(int i=0;i<n;i++){
		if(a[i].x<=b){
			sum+=a[i].y;
			b-=a[i].x;
		}
		else{
			sum+=b*a[i].y/a[i].x;
			break;
		}
	}
	printf("%.2lf",sum);
}