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来源：互联网发布：二选一数据选择器编辑：程序博客网时间：2024/05/16 14:06

很简单的贪心，写一个结构体，按j/f的比例从大到小排，有限选择比例大的就行，注意要用double，float可能精度不够第一次WA了。

#include <iostream>#include <cstdio>#include <cstring>#include <string>#include <map>#include <algorithm>#include <cmath>#include <iomanip>#include <vector>#include <stack>#include <cstdlib>#include <queue>#include <set>#include <cctype>using namespace std;#define  loop(i,u,v) for(int i = u;i <= v;i++)#define rloop(i,u,v) for(int i = u;i >= v;i--)#define eps  0.00000001typedef long long ll;struct stu{    int x;    int y;} jf[10001];bool cmp(stu a,stu b){    float rate1 = (float)a.x / a.y;    float rate2 = (float)b.x / b.y;    return rate1 > rate2;}int main(){    int n,m;    while(cin >> n >> m)    {        if(n == -1)            break;        loop(i,1,m)            scanf("%d%d",&jf[i].x,&jf[i].y);        sort(jf+1,jf+1+m,cmp);        double sum = 0;         loop(i,1,m)        {            if(n <= 0)                break;            else if((double)n >= jf[i].y)            {                sum += (double)jf[i].x;                n -= jf[i].y;            }            else            {                sum += (double) jf[i].x / jf[i].y * n;                break;            }        }        printf("%.3lf\n",sum );    }    return 0;}

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