poj3262 Protecting the Flowers

思路：

简单贪心，每次选择性价比最高的。

实现：

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <algorithm>
 4 using namespace std;
 5
 6 struct node
 7 {
 8     int t, d;
 9 };
10 int n;
11 node a[100005];
12 int sum[100005];
13
14 bool cmp(const node & a, const node & b)
15 {
16     double x = a.d * 1.0 / a.t;
17     double y = b.d * 1.0 / b.t;
18     return x > y;
19 }
20
21 int main()
22 {
23     cin >> n;
24     for (int i = 0; i < n; i++)
25     {
26         scanf("%d %d", &a[i].t, &a[i].d);
27     }
28     sort(a, a + n, cmp);
29     sum[n - 1] = a[n - 1].d;
30     for (int i = n - 2; i >= 0; i--)
31     {
32         sum[i] = sum[i + 1] + a[i].d;
33     }
34     long long total = 0;
35     for (int i = 0; i < n - 1; i++)
36     {
37         total += sum[i + 1] * 2 * a[i].t;
38     }
39     cout << total << endl;
40     return 0;
41 }