Solution for Grid Problems 1 (https://youtu.be/9DyQTftdiBY)

Rotate.java

import java.util.*;
public class Rotate {

  static final int BLANK = 0;
  static final int RED = 1;
  static final int BLUE = 2;

  static Scanner sc = new Scanner(System.in);
    
  public static void main(String[] args) {
  
    int t = Integer.valueOf(sc.nextLine());

    for (int i = 1; i <= t; i++) {

      String[] line = sc.nextLine().split(" +");
      int n = Integer.valueOf(line[0]);
      int k = Integer.valueOf(line[1]);

      int[][] grid = new int[n][n];

      // read in the NxN grid

      for (int y = 0; y < n; y++) {
        String str = sc.nextLine();
        for (int x = 0; x < n; x++) {
          switch (str.charAt(x)) {

            case '.':
              grid[y][x] = BLANK;
              break;

            case 'R':
              grid[y][x] = RED;
              break;

            case 'B':
              grid[y][x] = BLUE;
              break;

          }
        }
      }

      // shift all R's and B's to the right
      grid = gravityToRight(grid, n);

      // find the winners
      boolean redHasWon = isWinning(grid, n, k, RED);
      boolean blueHasWon = isWinning(grid, n, k, BLUE);

      // print result
      String result;
      if (blueHasWon && redHasWon)
        result = "Both";
      else if (blueHasWon)
        result = "Blue";
      else if (redHasWon)
        result = "Red";
      else
        result = "Neither";

      System.out.printf("Case #%d: %s\n", i, result);

    }


  }


  static int[][] gravityToRight(int[][] grid, int n) {

    int[][] newGrid = new int[n][n];

    // row by row
    for (int y = 0; y < n; y++) {

      // shift them over from right to left
      int shiftedX = n - 1;
      for (int x = n - 1; x >= 0; x--) {
        if (grid[y][x] != BLANK)
          newGrid[y][shiftedX--] = grid[y][x];
      }

    }

    return newGrid;

  }

  static boolean isWinning(int[][] grid, int n, int k, int piece) {

    for (int i = 0; i < n; i++) {

      // vertical
      if (countPiecesInRow(grid, piece, i, 0, 0, 1, n) >= k)
        return true;

      // horizontal
      if (countPiecesInRow(grid, piece, 0, i, 1, 0, n) >= k)
        return true;

      // diagonal (bottom left to top right)
      if (countPiecesInRow(grid, piece, 0, i, 1, -1, n) >= k)
        return true;
      if (countPiecesInRow(grid, piece, i, n-1, 1, -1, n) >= k)
        return true;

      // diagonal (top left to bottom right)
      if (countPiecesInRow(grid, piece, i, 0, 1, 1, n) >= k)
        return true;
      if (countPiecesInRow(grid, piece, 0, i, 1, 1, n) >= k)
        return true;

    }

    return false;

  }

  static int countPiecesInRow(int[][] grid, int piece, int x, int y, int dx, int dy, int n) {

    int max = 0;
    int counter = 0;

    while (x >= 0 && y >=0 && x < n && y < n) {

      if (grid[y][x] == piece) {
        counter++;
        max = Math.max(max, counter);
      } else {
        counter = 0;
      }

      x += dx;
      y += dy;

    }

    return max;

  }

}