Pass array; transpose 3×3 matrix

Passing an array to a function

Only the array name is written in the function call, for example transpose(a, t);. The name gives the address of the first element, so the called function works on the original array (call by reference) and no copy is made. The parameter is declared as an array (int a[3][3], or int a[][3]); for 2D arrays the column size is compulsory. Changes made to the array inside the function are visible in the caller.

Program

Both matrices are read in main() and passed to the function transpose(a, t), which stores a[i][j] in t[j][i]. The transposed matrices are then displayed from main().

#include <stdio.h>

void transpose(int a[3][3], int t[3][3])
{
    for (int i = 0; i < 3; i++)
        for (int j = 0; j < 3; j++)
            t[j][i] = a[i][j];
}

int main(void)
{
    int a[3][3], b[3][3], ta[3][3], tb[3][3];
    printf("Enter first matrix (9 values): ");
    for (int i = 0; i < 3; i++)
        for (int j = 0; j < 3; j++)
            scanf("%d", &a[i][j]);
    printf("Enter second matrix (9 values): ");
    for (int i = 0; i < 3; i++)
        for (int j = 0; j < 3; j++)
            scanf("%d", &b[i][j]);

    transpose(a, ta);
    transpose(b, tb);

    printf("Transpose of first matrix:\n");
    for (int i = 0; i < 3; i++) {
        for (int j = 0; j < 3; j++)
            printf("%4d", ta[i][j]);
        printf("\n");
    }
    printf("Transpose of second matrix:\n");
    for (int i = 0; i < 3; i++) {
        for (int j = 0; j < 3; j++)
            printf("%4d", tb[i][j]);
        printf("\n");
    }
    return 0;
}

Sample run

Input: 1 2 3 4 5 6 7 8 9 9 8 7 6 5 4 3 2 1

Enter first matrix (9 values): Enter second matrix (9 values): Transpose of first matrix:
   1   4   7
   2   5   8
   3   6   9
Transpose of second matrix:
   9   6   3
   8   5   2
   7   4   1