洛谷P4526 【模板】自适应辛普森法2(simpson积分)

2.33

1.51068

// luogu-judger-enable-o2
#include<cstdio>
#include<cmath>
double a;
double F(double x) {
    return pow(x, a / x - x);
}
double sim(double l, double r) {
    return (F(l) + F(r) + 4 * F((l + r) / 2)) * (r - l) / 6;
}
double asr(double L, double R, double eps, double ans) {
    double mid = (L + R) / 2;
    double LL = sim(L, mid), RR = sim(mid, R);
    if(fabs(LL + RR - ans) <= 15 * eps) return LL + RR;
    return asr(L, mid, eps / 2, sim(L, mid)) + asr(mid, R, eps / 2, sim(mid, R));
}
main() {
    #ifdef WIN32
    freopen("a.in", "r", stdin);
    #endif
    scanf("%lf", &a);
    if(a < 0) {printf("orz");return 0;}
    printf("%.5lf", asr(1e-9, 20, 1e-7, sim(0, 20)));
}