(4.4E)FatMouse‘s Trade (贪心算法)

题目：

样例：

 代码：

#include<stdio.h>
#include<algorithm>
using namespace std;
struct room{
	double j;
	double f;
	double rate;
}rooms[1010];
bool cmp(room a,room b){
	return a.rate>b.rate;
}
int main(){
	double m;
	int n;
	while(1){
		scanf("%lf%d",&m,&n);
		if(m==-1||n==-1){
			break;
		}
		for(int i=0;i<n;i++){ 
			scanf("%lf%lf",&rooms[i].j,&rooms[i].f);
			rooms[i].rate=rooms[i].j/rooms[i].f;
		}
		sort(rooms,rooms+n,cmp);
		double rest=m;//还能选择的猫粮
		int k;
		double maxfood=0;
		for(int i=0;i<n;i++){
		    if(rest>rooms[i].f){
		       	rest=rest-rooms[i].f;
		       	maxfood+=rooms[i].j;	
		    }
			else if(rest<=rooms[i].f){
				maxfood+=rest*rooms[i].rate;
				break;	
			}
		}
		printf("%.3f\n",maxfood);
		
	}
	return 0;
}