是否加满油

https://www.acwing.com/problem/content/1519/

#include <iostream>
#include <cstring>
#include <algorithm>

using namespace std;

const int N = 510;

int c_max, d, d_avg, n;
struct Stop
{
    double p, d;

    bool operator< (const Stop& t) const
    {
        return d < t.d;
    }
}s[N];

int main()
{
    cin >> c_max >> d >> d_avg >> n;
    for (int i = 0; i < n; i ++ ) cin >> s[i].p >> s[i].d;
    s[n] = {0, (double)d};

    sort(s, s + n + 1);

    if (s[0].d)
    {
        puts("The maximum travel distance = 0.00");
        return 0;
    }

    double res = 0, oil = 0;
    for (int i = 0; i < n;)
    {
        int k = -1;
        for (int j = i + 1; j <= n && s[j].d - s[i].d <= c_max * d_avg; j ++ )
            if (s[j].p < s[i].p)
            {
                k = j;
                break;
            }
            else if (k == -1 || s[j].p < s[k].p)
                k = j;

        if (k == -1)
        {
            printf("The maximum travel distance = %.2lf\n", s[i].d + (double)c_max * d_avg);
            return 0;
        }

        if (s[k].p <= s[i].p)
        {
            res += ((s[k].d - s[i].d) / d_avg - oil) * s[i].p;
            i = k;
            oil = 0;
        }
        else
        {
            res += (c_max - oil) * s[i].p;
            oil = c_max - (s[k].d - s[i].d) / d_avg;
            i = k;
        }
    }

    printf("%.2lf\n", res);

    return 0;
}