题解

题解

#include <bits/stdc++.h>

using namespace std;
struct jiazhi{
    double mn,w;
}* x;//动态数组
bool cmp(jiazhi a,jiazhi b){return a.mn/a.w>b.mn/b.w;}//用“单价”排序，从大到小

double da() {
    double cnt=0;
    int w,s;
    cin >>w>>s;
    x=new jiazhi[s+5];
    for(int i=1;i<=s;i++) cin >> x[i].w >> x[i].mn;
    sort(x+1,x+s+1,cmp);
    for(int i=1;i<=s;i++){
        if(x[i].w<=w){
            cnt+=x[i].mn;
            w-=x[i].w;
        }else{
            cnt+=x[i].mn*1.0/x[i].w*w;
            break;
        }
    }
    
    return cnt;
}
int main(){
    int n;
    cin >> n;
    while(n--){
        printf("%.2lf\n",da());
    }
    return 0;
}