Skip to main content

Singly Linked List

def search(head, x):
    curr = head
    i = 0
    while curr:
        if curr.val == x:
            return i
        i += 1
        curr = curr.next
    return -1

Insert at beginning​

def insertAtBeginning(head, x):
    t = Node(x)
    t.next = head
    return t

Insert at end​

def insertAtEnd(head, x):
    if not head:
        return Node(x)
    curr = head
    while curr.next:
        curr = curr.next
    curr.next = Node(x)
    return head

Insert at index​

def insertAtIndex(head, x, p):
    t = Node(x)
    if p == 0:
        t.next = head 
        return t
    curr = head
    for i in range(p - 2):
        curr = curr.next
        if not curr:
            return head
    t.next = curr.next
    curr.next = t
    return head

Delete first​

def delFirst(head):
    if head:
        return head.next
    return None

Delete end​

def delEnd(head):
    if head == None or head.next == None:
        return None
    curr = head
    while curr.next.next:
        curr = curr.next
    curr.next = None
    return head