Hackerrank week code 27 - Hackonacci - matrix rotation - Java code - full score

weekcode27_Hackonacci_matrixrotation.java

import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {

    private static int rotation90(int[][] m) {
        int res = 0;
        int n = m.length;
        for (int i = 0; i < n / 2; i++) {
            for (int j = i; j < n - i - 1; j++) {
                //left to top
                res += (m[i][j] + m[n - 1 - j][i]) % 2;

                //bottom to left
                res += (m[n - 1 - j][i] + m[n - 1 - i][n - 1 - j]) % 2;

                //right to bottom
                res += (m[n - 1 - i][n - 1 - j] + m[j][n - 1 - i]) % 2;

                //top to right
                res += (m[j][n - 1 - i] + m[i][j]) % 2;
            }
        }
        return res;
    }

    private static int rotation180(int[][] m) {
        int res = 0;
        int n = m.length;
        for (int i = 0; i < n / 2; i++) {
            for (int j = i; j < n - i - 1; j++) {
                // switch top and bottom values
                res += ((m[i][j] + m[n - 1 - i][n - 1 - j]) % 2)*2;

                // switch left and right values
                res += ((m[n - 1 - j][i] + m[j][n - 1 - i]) % 2)*2;
            }
        }
        return res;
    }

    private static int rotation270(int[][] m) {
        int res = 0;
        int n = m.length;
        for (int i = 0; i < n / 2; i++) {
            for (int j = i; j < n - i - 1; j++) {
                //right to top
                res += (m[i][j] + m[j][n - 1 - i]) % 2;

                //bottom to right
                res += (m[j][n - 1 - i] + m[n - 1 - i][n - 1 - j]) % 2;

                //left to bottom
                res += (m[n - 1 - i][n - 1 - j] + m[n - 1 - j][i]) % 2;

                //top to left
                res += (m[n - 1 - j][i] + m[i][j]) % 2;
            }
        }
        return res;
    }

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        int q = in.nextInt();
        int[] r = {1, 1, 0, 1, 0, 0, 1};
        int[][] m = new int[n][n];
        for (int i = 0; i < n; i++) {
            int im2 = ((i + 1) % 7) * ((i + 1) % 7);
            for (int j = 0; j <= i; j++) {
                int jm = (j + 1) % 7;
                int v = im2 * jm * jm;
                m[i][j] = r[v % 7];
                m[j][i] = m[i][j];
            }
        }
        int[] sol = {0, rotation90(m), rotation180(m), rotation270(m)};

        for (int i = 0; i < q; i++) {
            int a = (in.nextInt() % 360) / 90;
            System.out.println(sol[a]);
        }
    }
}