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
1 #include<cstdio> 2 #include<cstring> 3 #include<iostream> 4 #include<algorithm> 5 #include<string> 6 #include<cmath> 7 #include<set> 8 #include<queue> 9 #include<map> 10 #include<stack> 11 #include<vector> 12 #include<list> 13 #include<deque> 14 #include<sstream> 15 #include<cctype> 16 #define REP(i, n) for(int i = 0; i < (n); i++) 17 #define FOR(i, s, t) for(int i = (s); i < (t); i++) 18 #define MEM(a, x) memset(a, x, sizeof(a)); 19 #define DEBUG(x) cout<<x<<endl; 20 #define DBG cout<<"----------------"<<endl; 21 #define mid(x, y) x + (y - x)/ 2 22 #define lc o<<1 23 #define rc o<<1|1 24 using namespace std; 25 typedef int64_t INT; 26 typedef long long ll; 27 typedef unsigned long long ull; 28 typedef pair<int, int> Pair; 29 const int maxn = 1e3 + 10; 30 const double eps = 1e-10; 31 const int INF = 1 << 30; 32 const int dir[4][2] = {1,0,0,1,0,-1,-1,0}; 33 const double pi = 3.1415926535898; 34 int T, n, m, cases; 35 struct node 36 { 37 double j, f; 38 bool operator < (const node& a)const 39 { 40 return (j / f) > (a.j / a.f); 41 } 42 }; 43 node a[maxn]; 44 int main() 45 { 46 while(cin >> m >> n) 47 { 48 if(m == -1 && n == -1)break; 49 memset(a, 0, sizeof(a)); 50 for(int i = 0; i < n; i++) 51 { 52 cin >> a[i].j >> a[i].f; 53 } 54 sort(a, a + n); 55 double ans = 0; 56 for(int i = 0; i < n; i++) 57 { 58 if(m >= a[i].f) 59 { 60 ans += a[i].j; 61 m -= a[i].f; 62 } 63 else 64 { 65 ans += (m * a[i].j / a[i].f); 66 break; 67 } 68 } 69 printf("%.3f\n", ans); 70 } 71 return 0; 72 }