Competitive-Programming/Clockwise712.cpp at master · srinivas9804/Competitive-Programming · GitHub

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#include <iostream>
#include <cstdlib>
#include <math.h>
#include <stack>
#include <algorithm>
using namespace std;
class Point {
public:
	int x, y;
	Point(int a, int b);
	Point();
};
Point::Point(int a, int b) {
	x = a;
	y = b;
}
Point::Point() {
	x = y = 0;
}
int determinant(Point p1, Point p2) {
	return p1.x*p2.y - p2.x*p1.y;
}
double distance(Point p1, Point p2) {
	return sqrt(pow(p2.x - p1.x, 2) + pow(p2.y - p1.y, 2));
}
int AntiClockwise(Point p1, Point p2, Point p3) {
	int val = determinant(p1, p2) + determinant(p2, p3) + determinant(p3, p1);
	if (val > 0)
		return 1;
	else if (val < 0)
		return -1;
	return 0;
}
Point smallest;
int compare(const void* a, const void* b) {
	Point* p1 = (Point*)a;
	Point* p2 = (Point*)b;
	int angle = AntiClockwise(smallest, *p1, *p2);
	if (angle < 0)
		return 1;
	else if (angle > 0)
		return -1;
	else {
		if (distance(smallest, *p2) > distance(smallest, *p1)) {
			return -1;
		}
		else
			return 1;
	}
}
int compare1(const void* a, const void* b) {
	Point* p1 = (Point*)a;
	Point* p2 = (Point*)b;
	int angle = AntiClockwise(smallest, *p1, *p2);
	if (angle < 0)
		return -1;
	else if (angle > 0)
		return 1;
	else {
		if (distance(smallest, *p2) > distance(smallest, *p1)) {
			return -1;
		}
		else
			return 1;
	}
}
bool onSegment(Point p, Point q, Point r) {
	if (q.x <= max(p.x, r.x) && q.x >= min(p.x, r.x) && q.y <= max(p.y, r.y) && q.y >= min(p.y, r.y))
		return true;
	return false;
}
int main() {
	Point points[300];
	int n;
	while (cin >> n) {
		if (n == 0)
			break;
		for (int i = 0; i < n; i++)
			cin >> points[i].x >> points[i].y;
		int ctr = 0;
		stack<Point> s;
		s.push(points[0]);
		s.push(points[1]);
		for (int i = 2; i <n; i++) {
			Point tmp = s.top();
			s.pop();
			Point tmp2 = s.top();
			s.pop();
			if (AntiClockwise(tmp, tmp2, points[i]) < 0) {// clockwise
				ctr++;
				s.push(tmp);
				s.push(tmp2);
			}
			if (AntiClockwise(tmp, tmp2, points[i]) == 0 && !onSegment(tmp, points[i], tmp2)) {//angle is 0
				ctr++;
				s.push(tmp);
				s.push(tmp2);
			}
			else {
				s.push(tmp2);
				s.push(points[i]);
			}
		}
		s = stack<Point>();
		s.push(points[0]);
		s.push(points[1]);
		int ctr1 = 0;
		for (int i = 2; i < n; i++) {
			Point tmp = s.top();
			s.pop();
			Point tmp2 = s.top();
			s.pop();
			if (AntiClockwise(tmp, tmp2, points[i]) > 0) {//anticlockwise
				ctr1++;
				s.push(tmp);
				s.push(tmp2);
			}
			if (AntiClockwise(tmp, tmp2, points[i]) == 0 && onSegment(tmp, points[i], tmp2)) {// angle is 180
				ctr1++;
				s.push(tmp);
				s.push(tmp2);
			}
			else {
				s.push(tmp2);
				s.push(points[i]);
			}
		}
		if (ctr < ctr1) {
			if (ctr == 0) {
				cout << "CC" << endl;
			}
			else
				cout << "Remove " << ctr << " bead(s), " << "CC" << endl;
		}
		else {
			if (ctr1 == 0) {
				cout << "C" << endl;
			}
			else
				cout << "Remove " << ctr1 << " bead(s), " << "C" << endl;
		}
	}
	return 0;
}