Submission #230820

#	Time	Username	Problem	Language	Result	Execution time	Memory
230820		walnutwaldo20	Relay (COI16_relay)	C++14	0 / 100	5 ms	384 KiB

relay

#include <bits/stdc++.h>

#define F0R(i, a) for (int i = 0; i < (int)(a); i++)

#define PB push_back
#define MP make_pair
#define X real()
#define Y imag()

#define F first
#define S second

using namespace std;

typedef long long ll;
typedef long double ld;

typedef complex<ld> point;
typedef pair<point, point> edge;

#define MAXN 100000

bool reaches[MAXN];

edge rev(edge e) { return MP(e.S, e.F); }

ll crossp(point p1, point p2) {
    return (conj(p1) * p2).Y;
}

ll dotp(point p1, point p2) {
    return (conj(p1) * p2).X;
}

bool rightof(point p, edge e) {
    bool ret = crossp(e.S - e.F, p - e.S) <= 0;
    return ret;
}

point get(vector<point>& v, int idx) {
    return v[(idx % (int)v.size() + (int)v.size()) % (int)v.size()];
}

bool inside(point p, vector<point>& hull) {
    F0R(i, hull.size()) {
        edge e = MP(hull[i], get(hull, i + 1));
        if (rightof(p, e)) {
            return false;
        }
    }
    return true;
}

point findtangent(vector<point>&hull, point p, bool seen1, bool seen2) {
    F0R(i, hull.size()) {
        edge edge1 = MP(get(hull, i - 1), hull[i]);
        edge edge2 = MP(hull[i], get(hull, i + 1));
        if (rightof(p, edge1) == seen1 && rightof(p, edge2) == seen2) {
            return hull[i];
        }
    }
    cout << "this should not print" << endl;
    exit(0);
}

ld cosbw(point e1, point e2) {
    ld res = dotp(e1, e2);
    res /= abs(e1);
    res /= abs(e2);
    return res;
}

edge findfarthest(vector<point>& candidates, edge tangent, int dir, vector<point>& hull) {
    int idx = 0;
    F0R(i, hull.size()) if (hull[i] == tangent.S) {
        idx = i;
    }
    
    edge res = MP(candidates[0], tangent.S);
    ld mincos = 1;
    for (const point p : candidates) {
        /*edge prevedge = MP(get(hull, idx - dir), hull[idx]);
        if (dir < 0) {
            prevedge = rev(prevedge);
        }
        if (!rightof(p, prevedge)) {
            continue;
        }*/
        
        edge curr = MP(p, hull[idx]);
        while (1) {
            edge e = MP(hull[idx], get(hull, idx + dir));
            if (dir < 0) {
                e = rev(e);
            }
            if (rightof(p, e)) {
                idx = ((idx + dir) % hull.size() + hull.size()) % hull.size();
                curr = MP(p, get(hull, idx));
                res = curr;
            } else {
                break;
            }
        }
        
        /*ld c = cosbw(curr.S - curr.F, tangent.S - tangent.F);
        if (c < mincos) {
            res = curr;
            mincos = c;
        }*/
        // res = curr;
    }
    return res;
}

void read(int& len, vector<point>& vec) {
    cin >> len;
    F0R(i, len) {
        ll x, y;
        cin >> x >> y;
        vec.PB(point(x, y));
    }
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    int n, m;
    vector<point> v, hull;
    read(n, v);
    read(m, hull);
    
    point righttangent = findtangent(hull, v[0], true, false);
    point lefttangent = findtangent(hull, v[0], false, true);
    
    vector<point> triangle;
    triangle.PB(v[0]);
    triangle.PB(righttangent);
    triangle.PB(lefttangent);
    
    vector<point> leftpoints, rightpoints;
    F0R(i, v.size()) {
        if (inside(v[i], triangle)) {
            reaches[i] = true;
        }
        if (rightof(v[i], MP(v[0], righttangent))) {
            reaches[i] = true;
            rightpoints.PB(v[i]);
        }
        if (rightof(v[i], MP(lefttangent, v[0]))) {
            reaches[i] = true;
            leftpoints.PB(v[i]);
        }
    }
    
    edge farthestleft = findfarthest(leftpoints, MP(v[0], lefttangent), -1, hull);
    edge farthestright = findfarthest(rightpoints, MP(v[0], righttangent), 1, hull);
    
    vector<point> lefttriangle;
    lefttriangle.PB(farthestleft.F);
    lefttriangle.PB(lefttangent);
    lefttriangle.PB(farthestleft.S);
    
    vector<point> righttriangle;
    righttriangle.PB(farthestright.F);
    righttriangle.PB(farthestright.S);
    righttriangle.PB(righttangent);
    
    F0R(i, v.size()) {
        if (rightof(v[i], rev(farthestleft))) {
            reaches[i] = true;
        }
        if (rightof(v[i], farthestright)) {
            reaches[i] = true;
        }
        if (inside(v[i], lefttriangle)) {
            reaches[i] = true;
        }
        if (inside(v[i], righttriangle)) {
            reaches[i] = true;
        }
    }
    int res = 0;
    F0R(i, n) if (reaches[i]) {
        res++;
    }
    cout << res - 1 << endl;
}

Compilation message (stderr)

relay.cpp: In function 'edge findfarthest(std::vector<std::complex<long double> >&, edge, int, std::vector<std::complex<long double> >&)':
relay.cpp:80:8: warning: unused variable 'mincos' [-Wunused-variable]
     ld mincos = 1;
        ^~~~~~

• Subtask 1: 0 / 18
• Subtask 2: 0 / 19
• Subtask 3: 0 / 20
• Subtask 4: 0 / 43