Project Euler Problem 11

问题：

In the 2020 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 any direction (up, down, left, right, or diagonally) in the 2020 grid?

答案：70600674

#include
#include
#include

int main(void)
{
    int tmp = 0, i = 0, j = 0, max = 0;
    int a[20][20];
    FILE* in;
    if((in = fopen("1.dat", "r")) == NULL)
    {
        printf("Can't open data file!\n");
        exit(0);
    }

    //Initialize a[20][20]
    for(i = 0; i < 20; i++)
        for(j = 0; j < 20; j++)
            fscanf(in, "%d", &a[i][j]);
           
    //Horizonal
    for(i=0; i<20; i++)
        for(j=0; j<16; j++){
            tmp = a[i][j]*a[i][j+1]*a[i][j+2]*a[i][j+3];
            if(tmp>max)
                max = tmp;
        }
    //Vertical
    for(i=0; i<16; i++)
        for(j=0; j<20; j++){
            tmp = a[i][j]*a[i+1][j]*a[i+2][j]*a[i+3][j];
            if(tmp>max)
                max = tmp;
        }
    //Dialog
    for(i=0; i<16; i++)
        for(j=0; j<16; j++){
            tmp = a[i][j]*a[i+1][j+1]*a[i+2][j+2]*a[i+3][j+3];
            if(tmp>max)
                max = tmp;
        }
    //AntiDialog
    for(i=0; i<16; i++)
        for(j=3; j<20; j++){
            tmp = a[i][j]*a[i+1][j-1]*a[i+2][j-2]*a[i+3][j-3];
            if(tmp>max)
                max = tmp;
        }

    printf("The max is %d \n", max);
    return 0;
}


/* The answer is 70600674 */