Permutations without repetition C - c

Question

I have this code for permutation WITH repetition. Would anyone help to modify it to be WITHOUT repetition. I can't figure it out.
int array1[] = {1, 2, 3}; //array can be {1,1,2,3} for example also
int array2[3];
void permWithRep (int array1[], int array2[], int last, int index){
int i, len = last+1;
enter code here
for ( i=0; i<len; i++ )
{
array2[index] = array1[i] ;
if (index == last){
for(int i = 0; i < 3; i++) {
printf("%d ", array2[i]);
}
printf("\n");
}
else // Recur for higher indexes
permWithRep (array1, array2, last, index+1);
}
}
int main()
{
int len = sizeof(array1)/sizeof(int);
permWithRep (array1, array2, len-1, 0);
return 0;
}

Answer 1

I tested this on few inputs and it works.
There is certainly a better way to do it, but that's what i did:
#include <stdio.h>
int array1[] = {1, 2, 3}; //array can be {1,1,2,3} for example also
int array2[3];
int fixed[3];
void permWithRep(int array1[], int array2[],int fixed_index[], int size , int level){
if(level == size) return print_array(array2,size);
for(int k = 0; k< size; k++){
if(!is_present_in_fixed(fixed_index,level,k)){
fixed_index[level] = k;
array2[level] = array1[k];
permWithRep(array1,array2,fixed_index,size,level+1);
}
}
}
void print_array(int array[], int size){
for(int k = 0; k < size; k++)printf("%d ",array[k]);
printf("\n");
}
int is_present_in_fixed(int array[], int size, int element ){
for(int k =0; k<size;k++)
if(element == array[k]) return 1;
return 0;
}
int main()
{
int len = sizeof(array1)/sizeof(int);
permWithRep (array1, array2, fixed, len, 0);
return 0;
}
What I did:
Add an array (fixed_index[]) that keep track of the already visited indexes for one permutation.
In the loop, check if the index of current element belongs to the index already visited in that permutation (is_present_in_fixed(fixed_index,level,k)).
If so, it just skip that element (it does not enter the if statement).
Otherwise adds that element to the visited for that permutation and go on with recursive call.
When all array has been iterated on (level == size), just print the results contained in array2.