hdu1009 FatMouse' Trade---贪心

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=1009

题意：一共有n个房子，每个房子里有老鼠喜欢吃的javabeans,但是每个房间里的javabeans的价格不一样。老鼠用m元，问m元最多可以卖多少javabeans，其中每个房间里的javabeans可以被分割。

直接求单价，排序即可

 #include<cstdio>
 #include<cstring>
 #include<iostream>
 #include<algorithm>
 #include<string>
 #include<cmath>
 #include<set>
 #include<queue>
 #include<map>
 #include<stack>
 #include<vector>
 #include<list>
 #include<deque>
 #include<sstream>
 #include<cctype>
 #define REP(i, n) for(int i = 0; i < (n); i++)
 #define FOR(i, s, t) for(int i = (s); i < (t); i++)
 #define MEM(a, x) memset(a, x, sizeof(a));
 #define DEBUG(x) cout<<x<<endl;
 #define DBG cout<<"----------------"<<endl;
 #define mid(x, y) x + (y - x)/ 2
 #define lc o<<1
 #define rc o<<1|1
 using namespace std;
 typedef int64_t INT;
 typedef long long ll;
 typedef unsigned long long ull;
 typedef pair<int, int> Pair;
 const int maxn = 1e3 + ;
 const double eps = 1e-;
 const int INF =  << ;
 const int dir[][] = {,,,,,-,-,};
 const double pi = 3.1415926535898;
 int T, n, m, cases;
 struct node
 {
     double j, f;
     bool operator < (const node& a)const
     {
         return (j / f) > (a.j / a.f);
     }
 };
 node a[maxn];
 int main()
 {
     while(cin >> m >> n)
     {
         if(m == - && n == -)break;
         memset(a, , sizeof(a));
         for(int i = ; i < n; i++)
         {
             cin >> a[i].j >> a[i].f;
         }
         sort(a, a + n);
         double ans = ;
         for(int i = ; i < n; i++)
         {
             if(m >= a[i].f)
             {
                 ans += a[i].j;
                 m -= a[i].f;
             }
             else
             {
                 ans += (m * a[i].j / a[i].f);
                 break;
             }
         }
         printf("%.3f\n", ans);
     }
     return ;
 }