Segmentation fault (core dumped) in Quick Union Implementaion in C

Question

#include
#include
int *id,N;

main()
{
    FILE* file=fopen(\"a.txt\",\"r\");
    int i,p,q,c;
    fscanf(file,\"%d\",&N);

    id=(in         


        

Answer 1

I would guess this is the problem

root(int i)
{
    int p;  
    while(p!=(*(id+p)))   <-- p uninitialised 
        p=*(id+p);
    return(p);
}

because p is uninitialised but you are using it as an offset in a pointer dereference. Even if it is not THE reason it is still a big problem.

You have since edited the question to leave

root(int i)
{
    int i;  
    while(i!=(*(id+i)))  
        i=*(id+i);
    return(i);
}

in which you redeclare an i variable locally as well as a i variable passed as function parameter.