Explain the output of 2D array with nested loop code-CodePudding

#include <stdio.h>
int main()
{
    int i, j, k, px[] = { -2, -2, -1, -1, 1, 1, 2, 2 },
                 py[] = { -1, 1, -2, 2, -2, 2, -1, 1 };
    int cox[4][4] = { { 0 } };
    for (i = 0; i < 4; i  )
    {
        for (j = 0; j < 4; j  )
        {
            for (k = 0; k < 8; k  )
                if (((i   px[k]) >= 0 && (i   px[k]) < 4) &&
                    ((j   py[k]) >= 0 && (j   py[k]) < 4))
                    cox[i][j]  ;
            printf("%d\t", cox[i][j]);
        }
        printf("\n\n");
    }
}

I partially understand this nested loop. but i can't fully understand why its output in some part are 3 and why smiddle part are 4 but i understand why output of corner parts of this 2d array is 2.please explain me.

CodePudding user response：

As the result matrix is quadrant symmetric, let me start with examining the four cases: (i=0, j=0), (i=0, j=1), (j=1, i=0) and (i=1, j=1).

If (i=0, j=0), the condition (i px[k]) >= 0 && (i px[k]) < 4) && ((j py[k]) >= 0 && (j py[k]) < 4) meets twice: when k=5 and k=7.
If (i=0, j=1), the condition meets three times: when k=5, k=6 and k=7.
If (i=1, j=0), the condition meets three times: when k=3, k=5 and k=7.
If (i=1, j=1), the condition meets four times: when k=3, k=5, k=6 and k=7.

You can extend the similar consideration to the four quadrants then you can obtain the output.