poj3262 Protecting the Flowers

思路：

简单贪心，每次选择性价比最高的。

实现：

 #include <iostream>
 #include <cstdio>
 #include <algorithm>
 using namespace std;

 struct node
 {
     int t, d;
 };
 int n;
 node a[];
 int sum[];

 bool cmp(const node & a, const node & b)
 {
     double x = a.d * 1.0 / a.t;
     double y = b.d * 1.0 / b.t;
     return x > y;
 }

 int main()
 {
     cin >> n;
     for (int i = ; i < n; i++)
     {
         scanf("%d %d", &a[i].t, &a[i].d);
     }
     sort(a, a + n, cmp);
     sum[n - ] = a[n - ].d;
     for (int i = n - ; i >= ; i--)
     {
         sum[i] = sum[i + ] + a[i].d;
     }
     long long total = ;
     for (int i = ; i < n - ; i++)
     {
         total += sum[i + ] *  * a[i].t;
     }
     cout << total << endl;
     return ;
 }