Rotation

#include "bits/stdc++.h"
#include "graphics.h"

using namespace std;

#define PI                 2 * acos(0.0)
#define toRad(deg)         deg * PI / 180

struct Matrix
{
      int row;
      int col;
      double mat[4][4];

      Matrix(int row = 0, int col = 0) : row(row), col(col)
      {
            for (int i = 0; i < row; i++) for (int j = 0; j < col; j++) mat[i][j] = 0.0;
      }
      Matrix multiply(const Matrix &A, const Matrix &B)
      {
            Matrix C;
            C.row = A.row;
            C.col = B.col;
            for (int i = 0; i < A.row; i++)
            {
                  for (int j = 0; j < B.col; j++)
                  {
                        double sum = 0;
                        for (int k = 0; k < A.col; k++)
                        {
                              sum += A.mat[i][k] * B.mat[k][j];
                        }
                        C.mat[i][j] = sum;
                  }
            }
            return C;
      }
};

struct Point
{
      double x;
      double y;
      Point(double x = 0, double y = 0)
            : x(x)
            , y(y) {}
};

void rotat(vector <Point> &points, Point pivotPoint, double angle)
{
      // display object before Rotation
      setcolor(RED);
      line(points[0].x, points[0].y, points[1].x, points[1].y);
      line(points[1].x, points[1].y, points[2].x, points[2].y);
      line(points[0].x, points[0].y, points[2].x, points[2].y);

      Matrix rotaionMatrix(2, 2);
      rotaionMatrix.mat[0][0] = cos(toRad(angle));
      rotaionMatrix.mat[0][1] = -sin(toRad(angle));
      rotaionMatrix.mat[1][0] = sin(toRad(angle));
      rotaionMatrix.mat[1][1] = cos(toRad(angle));

      for (Point &p : points)
      {
            // Shifting the pivot point to the origin
            // and the given points accordingly
            Point shifted;
            shifted.x = p.x - pivotPoint.x;
            shifted.y = p.y - pivotPoint.y;

            Matrix shiftedMatrix(2, 1);
            shiftedMatrix.mat[0][0] = shifted.x;
            shiftedMatrix.mat[1][0] = shifted.y;

            Matrix rotatedMatrix = shiftedMatrix.multiply(rotaionMatrix, shiftedMatrix);

            Point rotatedPoint;
            rotatedPoint.x = rotatedMatrix.mat[0][0];
            rotatedPoint.y = rotatedMatrix.mat[1][0];

            // shift it back
            rotatedPoint.x = rotatedPoint.x + pivotPoint.x;
            rotatedPoint.y = rotatedPoint.y + pivotPoint.y;

            p.x = rotatedPoint.x;
            p.y = rotatedPoint.y;
      }
      // display object after rotation
      setcolor(GREEN);
      line(points[0].x, points[0].y, points[1].x, points[1].y);
      line(points[1].x, points[1].y, points[2].x, points[2].y);
      line(points[0].x, points[0].y, points[2].x, points[2].y);
}


signed main()
{
      freopen("rotation_in.txt", "r", stdin);

      vector <Point> points(3);
      for (Point &p : points) cin >> p.x >> p.y;
      Point pivotPoint;
      cin >> pivotPoint.x >> pivotPoint.y;
      double angle;
      cin >> angle;

      int gd = DETECT;
      int gm;
      detectgraph(&gd, &gm);
      initgraph(&gd, &gm, "");
      rotat(points, pivotPoint, angle);
      getch();
      closegraph();
}