题解

#include <bits/stdc++.h>
using namespace std;
const int size = 5e2+10; // 我crazy了
struct T {
    double p, f;
} a[size];
int N, last, in_min;
double F, C, D, P, res, now, Min, Y, Sum;
int main() {
    cin>>F>>C>>D>>P>>N;
    a[0].f = 0, a[0].p = P;
    res = C * D, now = 0, last = 0, Min = INT_MAX;
    if (!N) {	
        if (res < F) {
            cout<<"No solution";
            return 0;
        } else {
            cout<<fixed<<setprecision(2)<<F / D * P;
            return 0;
        }
    }
    for (int i = 1; i <= N; i++) {
        cin>>a[i].f>>a[i].p;
        if (a[i].f - a[i - 1].f > res) {	
            cout<<"No Solution";
            return 0;
        }
    }
    while (now <= F) {
        for (int i = last + 1; i <= N && a[i].f - a[last].f <= res; i++) {	
            if (a[i].p < Min) {
                Min = a[i].p;
                in_min = i;
                if (Min < a[last].p)
                    break;
            }
        }
        double temp = (a[in_min].f - a[last].f) / D; 
        if (Min < a[last].p) {
            if (temp <= Y) {
                Y -= temp;	
            } else {
                Sum += (temp - Y) * a[last].p;
                Y = 0;
            }
        } else {
            if (F - now <= res) {	
                Sum += ((F - now) / D - Y) * a[last].p;
                break;
            }
            Sum += (C - Y) * a[last].p;
            Y = C - temp;	
        }
        Min = INT_MAX;	
        last = in_min;		
        now = a[in_min].f;	
    }
    cout<<fixed<<setprecision(2)<<Sum;
    return 0;
}