[prev] 12 [next] 

  1. int temp = A[i];
A[i] = A[j];
A[j] = temp;


  2. NodeT *succ = head->next;
head->next = succ->next;
succ->next = head;
head = succ;


  3. x = StackPop(S);
y = StackPop(S);
StackPush(S, x);
StackPush(S, y);


The following pseudocode instruction is problematic. Why? 

...
swap the two elements at the front of queue Q
...