Line Segment Intersection

#include <bits/stdc++.h>

using namespace std;
using ll = long long;
typedef long long C;
typedef complex<C> P;
#define X real()
#define Y imag()

// Debug printing
#ifdef DEBUG
#define deb(fmt, args...) printf("DEBUG: %d: " fmt, __LINE__, ##args)
#define debug_print(fmt, args...) printf(fmt, ##args)
#else
#define deb(fmt, args...)
#define debug_print(fmt, args...)
#endif

void print_array(vector<int> in, const string title = "Vector")
{
	debug_print("DEBUG: %s [\nDEBUG: ", title.c_str());
	for (unsigned int i = 0; i < in.size(); i++) {
		debug_print("%d ", in[i]);
	}
	debug_print("\nDEBUG: ] END\n");
}

void print_matrix(vector<vector<int> > in, const string title = "Matrix")
{
	debug_print("DEBUG: %s [\nDEBUG: ", title.c_str());
	for (unsigned int i = 0; i < in.size(); i++) {
		for (unsigned int j = 0; j < in[i].size(); j++) {
			debug_print("%d ", in[i][j]);
		}
		debug_print("\nDEBUG: ");
	}
	debug_print("DEBUG: ] END\n");
}

int main(int argc, char *argv[])
{
	ios::sync_with_stdio(0);
	cin.tie(0);

	// Read the input parameters
	int n;
	cin >> n;

	double err = 0.000000001;

	for (int i = 0; i < n; i++) {
		int x1, y1, x2, y2;
		int x3, y3, x4, y4;
		cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3 >> x4 >> y4;
		P a = {x1, y1};
		// P b = {x2, y2};
		P c = {x3, y3};
		P d = {x4, y4};

		// Same endpoints
		if (a == c or a == d) {
			cout << "YES\n";
			continue;
		}

		double k = 1.0 * (y2 - y1) / (x2 - x1);
		double k2 = 1.0 * (y4 - y3) / (x4 - x3);

		// Same slopes, check if they overlap
		if (abs(k - k2) <= err) {
			int l = max(min(x1, x2), min(x3, x4));
			int r = min(max(x1, x2), max(x3, x4));
			double x = (y3 + k * x1 - y1) / k;
			if (x >= l && x <= r) {
				cout << "YES\n";
				continue;
			}
		}

		// Check if there is intersection
		double top = (-k * x1) + y1 + (k2 * x3) - y3;
		double x = top / (k2 - k);

		int l = max(min(x1, x2), min(x3, x4));
		int r = min(max(x1, x2), max(x3, x4));
		if (x >= l && x <= r) {
			cout << "YES\n";
			continue;
		}
		cout << "NO\n";
	}
}

Test 1

Verdict: WRONG ANSWER

Test 2

Verdict: WRONG ANSWER

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: WRONG ANSWER