Point in Polygon

#include <bits/stdc++.h>
using namespace std;
 
struct Point {
    double x, y;
    Point () { x = y = 0; }
    Point (double xx, double yy) { x = xx, y = yy; }
    void read() { cin >> x >> y; }
};
 
Point operator - (const Point& a, const Point& b) { return Point(a.x - b.x, a.y - b.y); }
Point operator + (const Point& a, const Point& b) { return Point(a.x + b.x, a.y + b.y); }
 
double cross(const Point& a, const Point& b) {
    return a.x * b.y - b.x * a.y;
}
 
// -1 -> ccw
int ccw(const Point& a, const Point& b, const Point& c) {
    Point ab = b - a;
    Point ac = c - a;
    int t = cross(ab, ac);
    
    if (t > 0) return -1;
    else if (t < 0) return 1;
    else return 0;
}
 
bool onseg(const Point& a, const Point& b, const Point& c) {
    return min(b.x, c.x) <= a.x && a.x <= max(b.x, c.x)
    &&     min(b.y, c.y) <= a.y && a.y <= max(b.y, c.y);
}
 
int inpoly(const vector<Point>& p, const Point& q) {
    int n = p.size();
    
    // check if point on edge
    for (int i = 0; i < n; i++) {
        Point u = p[i];
        Point v = p[(i + 1) % n];
        if (ccw(u, v, q) == 0 && onseg(q, u, v)) return 0;
    }
    
    // check if point inside
    bool ok = 0;
    for (int i = 0; i < n; i++) {
        Point u = p[i];
        Point v = p[(i + 1) % n];
        if (((u.y <= q.y && q.y < v.y) || (v.y <= q.y && q.y < u.y))
            && (q.x < u.x + (v.x - u.x) * (q.y - u.y) / (v.y - u.y)))
            ok = !ok;
    }
    
    if (ok) return 1;
    else return -1;
}
 
int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    
    int n, m;
    cin >> n >> m;
    
    vector<Point> p(n);
    for (int i = 0; i < n; i++) p[i].read();
    
    while (m--) {
        Point q;
        q.read();
        
        int ans = inpoly(p, q);
        if (ans == 1) cout << "INSIDE\n";
        else if (ans == -1) cout << "OUTSIDE\n";
        else cout << "BOUNDARY\n";
    }
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED