Detect Loop in a Linked List

Method 1: (Hashing)

bool detect_loop_map(Node *head){

    std::unordered_map<Node*, bool> visited;

    Node *curr = head;

    while(curr){

        if (visited[curr] == true)

            return true;

        visited[curr] = true;

        curr = curr->next;

    }

    return false;

}

Method 2:(Floyd's Cycle Detection)

bool detect_loop_floyd(Node *head){

    Node *slow = head;

    Node *fast = head;

    while(slow && fast && fast->next){

        slow = slow->next;

        fast = fast->next->next;

        if (slow == fast){

            return true;

        }

    }

    return false;

}

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