5 August

P1016 traveler's budget

Monotone queue.

Look at how a monotonous queue.

#include <cstdio>

int n, l, r;
double D, dd, d[9], C, p[9], ans;

struct node{
    double t, x;
} q[999];

int main() {
    scanf("%lf%lf%lf%lf%d", &D, &C, &dd, &p[0], &n); d[0]=0;
    for (int i=1; i<=n; ++i) {
        scanf("%lf%lf", &d[i], &p[i]);
        if (d[i]-d[i-1]>C*dd) {printf("No Solution\n"); return 0; }
    }
    d[n+1]=D; double now=0.0;
    q[++r]=(node){p[0], now=C}, ans+=p[0]*C;
    for (int i=1; i<=n+1; ++i) {
        double cos=(d[i]-d[i-1])/dd;
        while (l<=r && cos>0) {
            if (q[l].x>cos) {now-=cos, q[l].x-=cos; break; }
            now-=q[l].x, cos-=q[l].x; ++l;
        } 
        if (i==n+1) {
            while (l<=r) ans-=q[l].t * q[l].x, ++l; break;
        }
        while (l<=r && q[r].t>p[i]) {
            ans-=q[r].t*q[r].x, now-=q[r].x; --r;
        }
        ans+=(C-now)*p[i];
        q[++r]=(node){p[i], C-now}; now=C;
    } 
    printf("%.2lf\n", ans);
    return 0;
}