ZOJ 2109 FatMouse' Trade

  
    
/*
抄书上的程序..
用c语言写的老是WA
每次选效益最高的交换
*/
#include
< iostream >
#include
< fstream >
#include
< vector >
#include
< algorithm >
using namespace std;
struct Mouse
{
double j,f;
double shouyi;
};
bool comp( const Mouse & d1, const Mouse & d2){
if (d1.shouyi != d2.shouyi)
return d2.shouyi < d1.shouyi;
return d2.f > d1.f;
}
int main(){
// ifstream cin("2109.txt");
vector < Mouse > v;
Mouse mouse;
int m,n,i;
cout.precision(
3 ); // 三位小数
double sum;
while (cin >> m >> n){
if (m == - 1 && n == - 1 )
break ;
v.clear();
sum
= 0.0 ;
for (i = 0 ; i < n; ++ i){
cin
>> mouse.j >> mouse.f;
mouse.shouyi
= mouse.j / mouse.f;
v.push_back(mouse);
}
sort(v.begin(),v.end(),comp);
for (i = 0 ; i < v.size(); i ++ ){
if (m >= v[i].f){
sum
+= v[i].j;
m
-= ( int )v[i].f;
}
else {
sum
+= m * v[i].shouyi;
break ;
}
}
cout
<< fixed << sum << endl;
}
return 0 ;
}

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