C++ Interview Questions and Answers


Tell how to check whether a linked list is circular.

Create two pointers, each set to the start of the list. Update each as follows:

while (pointer1) {

pointer1 = pointer1->next;

pointer2 = pointer2->next; if (pointer2) pointer2=pointer2->next;

if (pointer1 == pointer2) {

print ("circularn");



OK, why does this work?

If a list is circular, at some point pointer2 will wrap around and be either at
the item just before pointer1, or the item before that. Either way, it’s either
1 or 2 jumps until they meet.

Posted by:Richards