hdu 1009 FatMouse' Trade - 贪心

[align=left]Problem Description[/align]

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.

[align=left]Input[/align]

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.

[align=left]Output[/align]

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.

[align=left]Sample Input[/align]

5 3
7 2
4 3
5 2
20 3
25 18
24 15
15 10
-1 -1

[align=left]Sample Output[/align]

13.333
31.500

[align=left]Author[/align]

CHEN, Yue

[align=left]Source[/align]
ZJCPC2004
[align=left]Recommend[/align]
JGShining
(转自hdu)

　　按照f / j排序
Code

/**
* acm.hdu.edu.cn
* Problem#1009
* Accepted
* Time:46ms
* Memory:1596k
*/
#include<iostream>
#include<cstdio>
#include<cctype>
#include<cstring>
#include<cstdlib>
#include<cmath>
#include<fstream>
#include<sstream>
#include<algorithm>
#include<map>
#include<set>
#include<queue>
#include<vector>
#include<stack>
using namespace std;
typedef bool boolean;
#define INF 0xfffffff
#define smin(a, b) a = min(a, b)
#define smax(a, b) a = max(a, b)
template<typename T>
inline void readInteger(T& u){
char x;
int aFlag = 1;
while(!isdigit((x = getchar())) && x != '-');
if(x == '-'){
x = getchar();
aFlag = -1;
}
for(u = x - '0'; isdigit((x = getchar())); u = (u << 1) + (u << 3) + x - '0');
ungetc(x, stdin);
u *= aFlag;
}

typedef class Data{
public:
int f;
int j;
double b;
}Data;

int n, m;
Data* datas;

inline boolean init() {
readInteger(n);
readInteger(m);
if(n == -1 && m == -1)    return false;
datas = new Data[(const int)(m + 1)];
for(int i = 1; i <= m; i++){
readInteger(datas[i].j);
readInteger(datas[i].f);
datas[i].b = datas[i].j * 1.0 / datas[i].f;
}
return true;
}

boolean cmpare(const Data& a, const Data& b){
return a.b > b.b;
}

double result;
inline void solve() {
result = 0.0;
sort(datas + 1, datas + m + 1, cmpare);
int i = 1;
while(n >= 0 && i <= m){
int buy = min(n, datas[i].f);
if(buy == datas[i].f)    result += datas[i].j;
else    result += buy * 1.0 / datas[i].f * datas[i].j;
n -= buy;
i++;
}
printf("%.3lf\n", result);
}

int main(){
while(init()){
solve();
delete[] datas;
}
return 0;
}