How to reflect a square matrix diagonally?

[keivi]

I have progressed to a point but I don't know what have I done wrong. Can you help me please?

#include <stdio.h>#include <conio.h>
int main ()
{
    int i, j, n, temp;
    printf ("Give the dimension: ");
    scanf("%d", &n);
    int matrix [n][n];
    for (i=0;i<n;i++)
    {
        for (j=0;j<n;j++)
        {
            printf ("\nGive element [%d][%d]: ", i, j);
            scanf ("%d", &matrix [i][j]);
        }}
    
    for (i=0;i<n;i++)
    {
        for (j=0;j<n;j++)
        printf ("%4d", matrix [i][j]);
        printf ("\n\n");
        }
  
 for (i=0;i<n;i++)
    {
        for (j=0;j<i;j++)
        {
            temp=matrix[i][j];
            matrix[i][j]=matrix [n-1-j][n-1-i];
            matrix[n-1-j][n-1-i]=temp;
            }
            }
           printf ("\n\n\n\n");
           for (i=0;i<n;i++)
    {
        for (j=0;j<n;j++)
        printf ("%4d", matrix [i][j]);
        printf ("\n\n");
        }
        getch ();
        return 0;
        }

[Adak]

Specify what type of reflection you want, with an example, and show what your program does now.

Save us time, and clear up possible misunderstandings.

For example:

1  2  3  Original matrix
4  5  6
7  8  9

to

9  6  3   45° right upper diagonal 
8  5  2   with no rotation
7  4  1

[rcgldr]

How to reflect a square matrix diagonally?

I'll assume you want to reflect the matrix by it's main diagonal (upper left to lower right). Note this is the same as transposing a matrix, so change your code to transpose a matrix.

[ZuK]

Generally your swap loop should run only to n/2. If they run to n you're swapping the elements twice and you end up with the original order.
Kurt

[rcgldr]

I used a fixed sized matrix and added some output to your example code to show what is being swapped and the intermediate states of the matrix. Compile and run this so you can see what is going on. Are you sure you want to reflect the matrix on the diagonal that goes from upper right to lower left?

#include <conio.h>
#include <stdio.h>

#define n 4

int matrix[n][n];
             
void showm(void)
{
int i, j;

    for(i = 0; i < n; i++){
        for(j = 0; j < n; j++){
            printf("%02x ", matrix[i][j]);
        }
        printf("\n");
    }
    printf("\n");
}

int main ()
{
int i, j, temp;

    for(i = 0; i < n; i++)
        for(j = 0; j < n; j++)
            matrix[i][j] = i * 0x10 + j;

    showm();

    for(i = 0; i < n; i++){
        for(j = 0; j < i; j++){
            printf("%d %d : %d %d\n", i, j, n-1-j, n-1-i);
            temp                 = matrix[i][j];
            matrix[i][j]         = matrix [n-1-j][n-1-i];
            matrix[n-1-j][n-1-i] = temp;
            showm();
        }
    }


    getch();
    return(0);
}

[rcgldr]

Just to be clear, this program is supposed to swap the elements of the same name as shown in this example?

a1 a2 a3 a4 xx
b1 b2 b3 xx a4
c1 c2 xx b3 a3
d1 xx c2 b2 a2
xx d1 c1 b1 a1