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Question

我被这个问题困住了。我确实认为我找到了正确的解决方案，但在将其提交到网站时，它不接受。

我尝试通过打印所有可能的组合来调试它，它们都已完成(水平、垂直和对角线)。该数组也已正确填充。我通过打印后检查了它。

你知道问题出在哪里吗？

问题

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

Project Euler

代码

String product = 
          "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 ";

Scanner sc = new Scanner(product);
int[][] in = new int[20][20];
for (int i = 0 ; i < 20 ; i++){
    for (int j = 0 ; j < 20 ; j++){
        in[i][j] = sc.nextInt();
    }
}

int max = Integer.MIN_VALUE;
int tmp = 0;

for (int i = 0 ; i < 20 ; i++){
    for (int j = 0 ; j < 20 ; j++){
        if (i < 17){
            tmp = in[i][j] * in[i+1][j] * in[i+2][j] * in[i+3][j];
            if (tmp > max) max = tmp;
        }
        if (j < 17){
            tmp = in[i][j] * in[i][j+1] * in[i][j+2] * in[i][j+3];
            if (tmp > max) max = tmp;
        }
        if (j < 17 && i < 17){
            tmp = in[i][j] * in[i+1][j+1] * in[i+2][j+2] * in[i+3][j+3];
            if (tmp > max) max = tmp;
        }
    }
}

System.out.println(max);

输出

51267216

Answer 1

你只检查了一条对角线，还需要检查另一条对角线:

if(j > 2 && i < 17) {
    tmp = in[i][j] * in[i+1][j-1] * in[i+2][j-2] * in[i+3][j-3];
    if (tmp > max) max = tmp;
}