1.1a.1i Introduction

Singly Linked List

We can initiate a singly linked list (SLList) as:

class Node:  
    def __init__(self, val, next):  # Initiates Node.  
        self.val = val  
        self.next = next  
  
  
class SLList:  
    def __init__(self, val):  # Initiates SLList.  
        self.head = Node(val, None)  
        self.size = 1  
  
    def __str__(self):  
        a = self  
        out = []
        while a.head:  
            out.append(a.head.val)  
            a.head = a.head.next  
        return str(out)  
  
    def size(self):  
        return self.size  
  
    def insert(self, val, pos=None):  
        if pos is None:  # Auto sets insert position to last position.  
            pos = self.size  
  
        if pos > self.size:  
            print("Index too large!")  
            return  
  
        a = self.head  # Removing abstraction barrier.  
        while pos - 1 > 0:  
            a = a.next  
            pos -= 1  
  
        a.next = Node(val, a.next)  
        self.size += 1