Problem11.java

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 /*
In the 20×20 grid below, four numbers along a diagonal line have been marked in red.

08 02 22 97 38 15 00 40 00 75 04 05 07 78 52 12 50 77 91 08
49 49 99 40 17 81 18 57 60 87 17 40 98 43 69 48 04 56 62 00
81 49 31 73 55 79 14 29 93 71 40 67 53 88 30 03 49 13 36 65
52 70 95 23 04 60 11 42 69 24 68 56 01 32 56 71 37 02 36 91
22 31 16 71 51 67 63 89 41 92 36 54 22 40 40 28 66 33 13 80
24 47 32 60 99 03 45 02 44 75 33 53 78 36 84 20 35 17 12 50
32 98 81 28 64 23 67 10 26 38 40 67 59 54 70 66 18 38 64 70
67 26 20 68 02 62 12 20 95 63 94 39 63 08 40 91 66 49 94 21
24 55 58 05 66 73 99 26 97 17 78 78 96 83 14 88 34 89 63 72
21 36 23 09 75 00 76 44 20 45 35 14 00 61 33 97 34 31 33 95
78 17 53 28 22 75 31 67 15 94 03 80 04 62 16 14 09 53 56 92
16 39 05 42 96 35 31 47 55 58 88 24 00 17 54 24 36 29 85 57
86 56 00 48 35 71 89 07 05 44 44 37 44 60 21 58 51 54 17 58
19 80 81 68 05 94 47 69 28 73 92 13 86 52 17 77 04 89 55 40
04 52 08 83 97 35 99 16 07 97 57 32 16 26 26 79 33 27 98 66
88 36 68 87 57 62 20 72 03 46 33 67 46 55 12 32 63 93 53 69
04 42 16 73 38 25 39 11 24 94 72 18 08 46 29 32 40 62 76 36
20 69 36 41 72 30 23 88 34 62 99 69 82 67 59 85 74 04 36 16
20 73 35 29 78 31 90 01 74 31 49 71 48 86 81 16 23 57 05 54
01 70 54 71 83 51 54 69 16 92 33 48 61 43 52 01 89 19 67 48

The product of these numbers is 26 × 63 × 78 × 14 = 1788696.

What is the greatest product of four adjacent numbers in the same direction (up, down, left, right, or diagonally) in the 20×20 grid?

 */
package problem11;

import java.util.Scanner;

public class Problem11 {

    public static void main(String[] args) {
        int[][] matrix = new int[20][20];
        try (Scanner scan = new Scanner(System.in)) {
            for (int i = 0; i < 20; i++) {
                for (int j = 0; j < 20; j++) {
                    matrix[i][j] = scan.nextInt();
                }
            }
            scan.close();
        }
        //Check correct input
        for (int i = 0; i < 20; i++) {
            for (int j = 0; j < 20; j++) {
                System.out.print(matrix[i][j] + " ");
            }
            System.out.println();
        }

        //columns
        int maxSum = 0;
        for (int i = 0; i < 20; i++) {
            for (int j = 0; j < 17; j++) {
                int temp = 1;
                int k = j;
                for (int counter = 1; counter <= 4; counter++) {
                    temp *= matrix[i][k];
                    k++;
                }
                maxSum = Math.max(maxSum, temp);
            }
        }
        //Rows
        for(int j = 0; j < 20; j++){
            for(int i = 0; i < 17; i++){
                int temp = 1;
                int k = i;
                for(int counter = 1; counter <= 4; counter++){
                    temp *= matrix[k][j];
                    k++;
                }
                maxSum = Math.max(maxSum, temp);
            }
        }

        //left diag
        for(int i = 0; i < 17; i++){
            for(int j = 0; j < 17; j++){
                int temp = 1;
                for(int counter = 0; counter < 4; counter++){
                    temp *= matrix[i+counter][j+counter];
                }
                maxSum = Math.max(temp, maxSum);
            }
        }

        //right diag
          for(int i = 0; i < 17; i++){
            for(int j = 3; j < 20; j++){
                int temp = 1;
                for(int counter = 0; counter < 4; counter++){
                    temp *= matrix[i + counter][j - counter];
                }
                maxSum = Math.max(temp, maxSum);
            }
        }
        System.out.println(maxSum);

    }


}