如何通过用户给出的输入将二维矩阵的元素打印为矩形

Question

I've come across this question in one of the assessments in our college. None of my friends were able to help me out. I even checked all leading online platforms for my desired output criteria. But no use, so I wanted to post my question in Stack Overflow.

I request people who are watching this tag to help me out. Even though my assessment has been completed, I'm eagerly trying to solve this problem but I couldn't.

#include <stdio.h>

int main()
{

     int a[4][4] = {{1, 2, 3, 4},
                    {5, 6, 7, 8},
                    {9, 10, 11, 12},
                    {13, 14, 15, 16}};

     int k, l, m, n, o, r;

     int temp[4][4] = {0};
     printf("Enter index of row & column: ");

     int p, q;
     scanf("%d %d", &p, &q);

     for (int i = p; i < 4; i++)
     {
          for (int j = q; j < 4; j++)
          {
               temp[i][j] = a[i][j];
               // initial given index number to left_most number
          }
          k = i + 1, l = 4 - q;

          for (k; k <= l; k++)
          {
               temp[k][l] = a[k][l];
               //rightmost element to bottom
          }
          m = k - 1, n = l - 1;

          for (n; n >= q; n--)
          {
               temp[m][n] = a[m][n];
               //bottomright to left elements upto the column index provided by user
          }
          o = m, r = q;

          for (o; o >= i + 1; o--)
          {
               temp[o][r] = a[o][r];
               //bottomleft to initial index element
          }
          break;
     }

     for (int i = 0; i < 4; i++)
     {
          for (int j = 0; j < 4; j++)
          {

               //if the element is zero then priting a space else printing the number
               if (temp[i][j] == 0)
               {
                    printf(" ");
               }

               else
               {
                    printf("%d ", temp[i][j]);
               }
          }
          printf("\n");
     }
     return 0;
}

Sample Input: Enter index of row & column: 0 1

Sample Output:

2  3  4
6     8
10    12
14 15 16

My code only works for sample input and the following column.

So I need help on how to make my code work for any input given by user, it has to print the zero(0) shape out of it.

Answer 1

There is a pretty neat solution to this problem

  for (int r = 0; r < numrows; r++) {
      for (int c = 0; c < numcols; c++) {
          if (r >= p && c >= q && 
             (c == q || c == numcols - 1 || r == p || r == numrows - 1)){
             printf("%2d ",a[r][c]);
          }
          else {
             printf("  ");
          }
       }
       printf("\n");
   }

where numrows = 4 and numcols = 4

Answer 2

For starters there is no need to declare an auxiliary array if the task is just to output a sub-array of the original array.

A straightforward approach in C can look the following way.

#include <stdio.h>

void rectangle_pattern( size_t n, int a[][n], size_t row, size_t col )
{
    for ( size_t i = row; i < n; ++i )
    {
        if ( i == row || i == n - 1 )
        {
            for ( size_t j = col; j < n; j++ )
            {
                printf( "%2d ", a[i][j] );
            }
        }
        else
        {
            printf( "%2d", a[i][col] );
            if ( col != n - 1 ) printf( "%*d", ( int )( 3 * ( n - col - 1 ) ), a[i][n-1] );
        }
        putchar( '\n' );
    }
}

int main(void) 
{
    enum { N = 4 };
    int a[N][N]= 
    { 
        {  1,  2,  3,  4 },
        {  5,  6,  7,  8 }, 
        {  9, 10, 11, 12 }, 
        { 13, 14, 15, 16 } 
    };

    size_t row = 0, col = 0;
    
    rectangle_pattern( N, a, row, col );
    
    putchar( '\n' );
    
    row = 0, col = 1;
    
    rectangle_pattern( N, a, row, col );
    
    putchar( '\n' );

    row = 0, col = 2;
    
    rectangle_pattern( N, a, row, col );
    
    putchar( '\n' );

    row = 0, col = 3;
    
    rectangle_pattern( N, a, row, col );
    
    putchar( '\n' );

    return 0;
}

The program output is

 1  2  3  4 
 5        8
 9       12
13 14 15 16 

 2  3  4 
 6     8
10    12
14 15 16 

 3  4 
 7  8
11 12
15 16 

 4 
 8
12
16 

The function declaration uses a variable length array as a parameter. You can change the function declaration declaring the parameter as having an array with a fixed size.