Find the starting node of a loop in a circularly linked list. **Important**

StartNodeCircularlyLinkedList.java

// Logical extension to hare-tortoise cycle detection algorithm
// first check for cycle using rabbit-tortoise algo then move back tortoise to head and advance both rabbit and 
//tortoise one by one
// The point where they meet will be the start of the loop
/**
 * Returns the node at the start of a loop in the given circular linked
 * list. A circular list is one in which a node's next pointer points
 * to an earlier node, so as to make a loop in the linked list. For
 * instance:
 *
 * input: A -> B -> C -> D -> E -> C [the same C as earlier]
 * output: C
 *
 * (CCI_0205)
 *
 * @param linkedList
 *            list to be tested
 * @return the node at the start of the loop if there is a loop, null
 * otherwise
 */
public static IntegerNode findLoopStart(LinkedList linkedList) {
    if (linkedList == null || linkedList.getHead() == null) {
        return null;
    }
 
    IntegerNode loopStartNode = null;
    IntegerNode slow = linkedList.getHead();
    IntegerNode fast = linkedList.getHead();
 
    while (slow != null && fast != null) {
        slow = slow.getNext();
        if (fast.getNext() == null) {
            loopStartNode = null;
            break;
        }
        fast = fast.getNext().getNext();
 
        // If slow and fast point to the same node, it means that the
        // linkedList contains a loop.
        if (slow == fast) {
 
            slow = linkedList.getHead();
 
            while (slow != fast) {
                // Keep incrementing the two pointers until they both
                // meet again. When this happens, both the pointers will
                // point to the beginning of the loop
                slow = slow.getNext(); // Can't be null, as we have a loop
                fast = fast.getNext(); // Can't be null, as we have a loop
            }
 
            loopStartNode = slow;// can be fast as well!!
            break;
        }
    }
 
    return loopStartNode;
}

Well done i was trying so hard to find a solution to this ty so much now i understand how it works by the way im only 16 year old boy, who loves to code and learn new stuff😅

Haha, happy to know it helped!

…

On Thu, Jan 2, 2020 at 12:54 PM baghdad11 ***@***.***> wrote: Well done i was trying so hard to find a solution to this ty so much now i understand how it works by the way im only 16 who loves to code and learn new stuff😅 — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <https://gist.github.com/6757839?email_source=notifications&email_token=AAK62MEOE4D6LJBAX7QL3VTQ3ZIBJA5CNFSM4KCGSGAKYY3PNVWWK3TUL52HS4DFVNDWS43UINXW23LFNZ2KUY3PNVWWK3TUL5UWJTQAF6ZHC#gistcomment-3125873>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAK62MHDKJ7HHS4ZBY445ALQ3ZIBJANCNFSM4KCGSGAA> .