hdu 1009贪心

水题，直接贴代码

/*

 * hdu1009/win.cpp

 * Created on: 2012-7-27

 * Author    : ben

 */

#include <cstdio>

#include <cstdlib>

#include <cstring>

#include <cmath>

#include <ctime>

#include <iostream>

#include <algorithm>

#include <queue>

#include <set>

#include <map>

#include <stack>

#include <string>

#include <vector>

#include <deque>

#include <list>

#include <functional>

#include <numeric>

#include <cctype>

using namespace std;

const int MAXN = 1005;

typedef struct Warehouse{

    double total;

    double need;

}Warehouse;

Warehouse wh[MAXN];

inline bool operator<(const Warehouse &wh1, const Warehouse &wh2) {

    return (wh1.total / wh1.need) > (wh2.total / wh2.need);

}



int main() {

#ifndef ONLINE_JUDGE

    freopen("data.in", "r", stdin);

#endif

    int N;

    double M, ans;

    while(scanf("%lf%d", &M, &N) == 2) {

        if(M == -1 && N == -1) {

            break;

        }

        for(int i = 0; i < N; i++) {

            scanf("%lf%lf", &wh[i].total, &wh[i].need);

        }

        sort(wh, wh + N);

        ans = 0;

        for(int i = 0; i < N; i++) {

            if(M <= 0) {

                break;

            }

            if(M >= wh[i].need) {

                ans += wh[i].total;

                M -= wh[i].need;

            }else {

                ans += M * wh[i].total / wh[i].need;

                M = 0;

            }

        }

        printf("%.3f\n", ans);

    }

    return 0;

}