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[100005];
int sum[100005];

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 = 0; i < n; i++)
    {
        scanf("%d %d", &a[i].t, &a[i].d);
    }
    sort(a, a + n, cmp);
    sum[n - 1] = a[n - 1].d;
    for (int i = n - 2; i >= 0; i--)
    {
        sum[i] = sum[i + 1] + a[i].d;
    }
    long long total = 0;
    for (int i = 0; i < n - 1; i++)
    {
        total += sum[i + 1] * 2 * a[i].t;
    }
    cout << total << endl;
    return 0;
}