C++ radix sort using doubly-linked list

Question

I am working on a program to sort a list of numbers using a radix sort but I keep getting stuck in what I think is an infinite loop. I think that it is either my main sort function or my counting function. Any ideas on what I am doing wrong?

void radix_sort(DLList& list)
{
  DLList lstRay[10];
  int ct = count(list);
  int zeros = 0;
  int tmp = 0;
  int head = 0;

  for(;ct >= 0; ct--)
  {
      while(!list.isEmpty())
      {
        head = list.deleteHead();
        tmp = head / pow(10, zeros);
        tmp = tmp % 10;
        lstRay[tmp].addToTail(head);
      }
      for(int x = 0; x <=9; x++)
      {
        list.append(lstRay[x]);
      }
      zeros++;   
   }      
}

int count(DLList& list)
{
  int ct = 0;
  int ct2 = 0;
  int tmp = 0;

  while(!list.isEmpty())
  {
      ct = ct2;
      tmp = list.deleteHead();
      while(tmp >= 0)
      {
        tmp = tmp/10;
        ct2++;
      }
      if(ct2 < ct)
      {
        ct2 = ct;
      }
    }
    return ct2;
}

Answer 1

You aren't clearing out lstRay on each iteration. This means when you loop around again, each lstRay is getting longer and longer, so your list is growing exponentially.

However, I am surprised that it gets that far - it looks like your count function will clear the list.

Answer 2

The infinite loop is inside count(). The loop on temp never terminates, because temp never gets below zero.

The radix_sort function has a problem too. listRay[tmp] is not initialised.