func.c

#include <stdio.h>

// function to print the array
void printarray(int arr[], int size)
{
    int i, j;
    for (i = 0; i < size; i++)
    {
        printf("%d\t", arr[i]);
    }
    printf("\n");
}

// function to swap the variables
void swap(int *a, int *b)
{
    int temp;
    temp = *a;
    *a = *b;
    *b = temp;
}

// permutation function
void permutation(int *arr, int start, int end)
{
    if (start == end)
    {
        printarray(arr, end + 1);

        return;
    }
    int i;
    for (i = start; i <= end; i++)
    {
        // swapping numbers
        swap((arr + i), (arr + start));
        // fixing one first digit
        // and calling permutation on
        // the rest of the digits
        permutation(arr, start + 1, end);
        swap((arr + i), (arr + start));
    }
}

int main()
{
    // taking input to the array
    int size;
    printf("Enter the size of array\n");
    scanf("%d", &size);
    int i;
     int arr[size];
    // for (i = 0; i < size; i++)
    //     scanf("%d", &arr[i]);
    // calling permutation function
    permutation(arr, 1, 4);
    return 0;
}