Point in Polygon

#include <iostream>
#include <vector>

using namespace std;

int main() {
    int n, m;
    cin >> n >> m;

    vector<pair<long long, long long>> vertices(n);
    
    for (int i = 0; i < n; ++i)
        cin >> vertices[i].first >> vertices[i].second;
    
    for (int i = 0; i < m; ++i) {
        long long x, y;
        cin >> x >> y;
        
        bool boundary = false;
        bool inside = false;
        
        for (int j = 0; j < n; ++j) {
            long long x1 = vertices[j].first;
            long long y1 = vertices[j].second;
            long long x2 = vertices[(j + 1) % n].first;
            long long y2 = vertices[(j + 1) % n].second;
            
            if ((y == y1 && y == y2 && x >= min(x1, x2) && x <= max(x1, x2)) || (x == x1 && x == x2 && y >= min(y1, y2) && y <= max(y1, y2))) {
                boundary = true;
                break;
            }
            
            if ((y1 > y) != (y2 > y)) {
                double x_intersect = (double)(x2 - x1) * (y - y1) / (y2 - y1) + x1;
                if (x_intersect == x) {
                    boundary = true;
                    break;
                }
                if (x_intersect > x)
                    inside = !inside;
            }
        }
    
        if (boundary)
            cout << "BOUNDARY" << endl;
        else if (inside)
            cout << "INSIDE" << endl;
        else 
            cout << "OUTSIDE" << endl;
    }
    
    return 0;
}

Test 1

Verdict: WRONG ANSWER

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