MaximumSumOfHourGlassInMatrix.java

public class MaximumSumOfHourGlassInMatrix {

  private static int[][] input1 = {
      {1, 2, 3, 4, 5},
      {0, 5, 1, 5, 2},
      {0, 0, 0, 1, 3},
      {4, 1, 1, 0, 1},
      {0, 0, 0, 0, 3},
  };

  private static int[][] input2 = {
      {3, 0, 0, 5},
      {2, 5, 5, 5},
      {0, 0, 0, 1},
      {4, 4, 0, 0},
      {0, 0, 3, 0},
  };


  private static int[][] input3 = {
      {-1, -1, 0, -9, -2, -2},
      {-2, -1, -6, -8, -2, -5},
      {-1, -1, -1, -2, -3, -4},
      {-1, -9, -2, -4, -4, -5},
      {-7, -3, -3, -2, -9, -9},
      {-1, -3, -1, -2, -4, -5}
  };

  public static void main(String args[]) {
    System.out.println("Max Sum for input1 is: " + findMaxSum(input1) + "\n");
    System.out.println("Max Sum for input2 is: " + findMaxSum(input2)+ "\n");
    System.out.println("Max Sum for input3 is: " + findMaxSum(input3)+ "\n");
  }

  private static int findMaxSum(int arr[][]) {
    int rowLength = arr.length;
    if (rowLength < 3) {
      System.err.println("Bad Input, row length must be 3 or more");
      return -1;
    }
    int colLength = arr[0].length;
    if (colLength < 3) {
      System.err.println("Bad Input, column length must be 3 or more");
      return -1;
    }

    int maxSum = Integer.MIN_VALUE;
    int tempMaxSum = Integer.MIN_VALUE;
    StringBuilder maxSumStr = new StringBuilder();
    String resultMaxSumStr = "";
    for (int i = 0; i < rowLength - 2; i++) {
      for (int j = 0; j < colLength - 2; j++) {
        int sum =
            arr[i][j]      + arr[i][j + 1]     +arr[i][j + 2]
                           + arr[i + 1][j + 1] +
            arr[i + 2][j]  +arr[i + 2][j + 1]  +arr[i + 2][j + 2];

        maxSum = Math.max(maxSum, sum);

        if (tempMaxSum < maxSum) {
          maxSumStr.append(arr[i][j]).append("   ").append(arr[i][j + 1]).append("   ")
              .append(arr[i][j + 2]).append("\n")
              .append("    ").append(arr[i + 1][j + 1]).append("\n")
              .append(arr[i + 2][j]).append("   ").append(arr[i + 2][j + 1]).append("   ")
              .append(arr[i + 2][j + 2]).append("\n\n");
          tempMaxSum = maxSum;
          resultMaxSumStr = maxSumStr.toString();
          maxSumStr = new StringBuilder();
        }
      }
    }
    System.out.print(resultMaxSumStr);
    return maxSum;
  }
}