[代码]ACM-ICPC 2012 Regionals Asia - Jinhua D Crazy Tank / HDU 4445

Abstract

ACM-ICPC 2012 Regionals Asia - Jinhua D Crazy Tank / HDU 4445

扫描线

Source

http://acm.hdu.edu.cn/showproblem.php?pid=4445

Solution

很多人是水过的，我贴个正经的扫描线的吧。

Code

#include <cassert>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <iostream>
#include <cmath>
using namespace std;

const double PI = acos(-1.0);
const double EPS = 1e-8;

inline int sgn(double x) {
    if (fabs(x)<EPS) return 0;
    return x>0?1:-1;
}

int N, M;
double l1, r1, l2, r2;
double v[222];
double g=9.8, h;

double calc(double v, double a) {
    double vx = v*cos(a);
    double vy = v*sin(a);
    double delta = vy*vy+2*g*h;
    delta = max(0.0, delta);
    double t = (vy+sqrt(delta))/g;
    return vx*t;
}

double tri(double l, double r, double v, double &d) {
    int cnt = 100;
    while (cnt--) {
        double m1 = (l+r)/2;
        double m2 = (m1+r)/2;
        if (calc(v, m1)>calc(v, m2)) r = m2;
        else l = m1;
    }
    d = calc(v, l);
    return l;
}

double bin(double l, double r, double d, double v, bool up) {
    int cnt = 100;
    while (cnt--) {
        double m = (l+r)/2;
        if ((calc(v, m)<d)^up) l = m;
        else r = m;
    }
    return l;
}

struct se {
    double a;
    bool in;
    int cnt;
    se() {}
    se(double x, bool y, int z): a(x), in(y), cnt(z) {}
    bool operator<(const se &rhs) const {
        if (sgn(a-rhs.a)==0) {
            return in<rhs.in;
        }
        return a<rhs.a;
    }
}e[9999];

void ae(double a, bool in, int cnt) {
    e[M++] = se(a, in, cnt);
}

void solve(double l, double r, double d, double v, double t, int cnt) {
    if (sgn(d-l)<0) return;
    if (sgn(d-r)<0) {
        double hmr = bin(-PI/2, t, l, v, 0);
        double mdk = bin(t, PI/2, l, v, 1);
        if (sgn(hmr-mdk)>0) while (1) puts("");
        ae(hmr, 0, cnt); ae(mdk, 1, -cnt);
        return;
    }
    double s1 = bin(-PI/2, t, l, v, 0);
    double t1 = bin(-PI/2, t, r, v, 0);
    double s2 = bin(t, PI/2, r, v, 1);
    double t2 = bin(t, PI/2, l, v, 1);
    if (sgn(s1-t1)>0) while (1) puts("");
    if (sgn(s2-t2)>0) while (1) puts("");
    if (sgn(t1-s2)>=0) {
        ae(s1, 0, cnt); ae(t2, 1, -cnt);
    }
    else {
            ae(s1, 0, cnt); ae(t1, 1, -cnt);
            ae(s2, 0, cnt); ae(t2, 1, -cnt);
    }
}

char s[111];

int main() {
    int i, j, k;
    while (cin>>N>>h>>l1>>r1>>l2>>r2, N) {
        M = 0;
        for (i = 0; i < N; ++i) {
            cin>>v[i];
            double d, t;
            t = tri(-PI/2, PI/2, v[i], d);
            solve(l1, r1, d, v[i], t, 1);
            solve(l2, r2, d, v[i], t, -998);
        }
        sort(e, e+M);
        int ans = 0;
        int cnt = 0;
        for (i = 0; i < M; ++i) {
            cnt += e[i].cnt;
            if (cnt>N) while (1) puts("");
            ans = max(ans, cnt);
        }
        printf("%d\n", ans);
    }
    return 0;
}