FatMouse' Trade
Problem Description
FatMouse prepared M pounds of cat food, ready to trade with the cats guarding the warehouse containing his favorite food, JavaBean.
The warehouse has N rooms. The i-th room contains J[i] pounds of JavaBeans and requires F[i] pounds of cat food. FatMouse does not have to trade for all the JavaBeans in the room, instead, he may get J[i]* a% pounds of JavaBeans if he pays F[i]* a% pounds of cat food. Here a is a real number. Now he is assigning this homework to you: tell him the maximum amount of JavaBeans he can obtain.
Input
The input consists of multiple test cases. Each test case begins with a line containing two non-negative integers M and N. Then N lines follow, each contains two non-negative integers J[i] and F[i] respectively. The last test case is followed by two -1's. All integers are not greater than 1000.
Output
For each test case, print in a single line a real number accurate up to 3 decimal places, which is the maximum amount of JavaBeans that FatMouse can obtain.
Sample Input
5 3
7 2
4 3
5 2
20 3
25 18
24 15
15 10
-1 -1
Sample Output
13.333
31.500
题意描述:
老鼠手里总共有n个房间,m个猫粮,每个房间不同数量的老鼠喜欢的食物,想要获得食物就要给猫猫粮。给出了每个房间的老鼠食物的食物量,及所对应需要的猫粮。可以给少于对应房间的猫粮,当然得到的食物也是对应比例的。求能获得最大喜欢食物的量。
解题思路:
简单的贪心,求出每个房间每个猫粮的价值,根据价值进行排序。从价值最大的开始换取,当不够把一个房间的食物换完是,换取对比例的食物。
程序代码:
#include<stdio.h>
#include<algorithm>
using namespace std;
struct A
{
int a;
int b;
double c;
}q[1010];
double cmp(struct A a,struct A b)
{
return a.c>b.c;
}
int main()
{
int n,m,i,j;
double sum;
while(scanf("%d%d",&m,&n))
{
if(m==-1&&n==-1)
break;
sum=0;
for(i=1;i<=n;i++)
{
scanf("%d%d",&q[i].b,&q[i].a);
q[i].c=q[i].b*1.0/q[i].a;
}
sort(q+1,q+n+1,cmp);
for(i=1;i<=n;i++)
{
if(q[i].a<=m)
{
m=m-q[i].a;
sum+=q[i].b;
}
else
{
sum+=m*q[i].c;
break;
}
}
printf("%.3f\n",sum);
}
return 0;
}