LinkedList

A linked list is a linear data structure, in which the elements are not stored at contiguous memory locations. The elements in a linked list are linked using pointers. In simple words, a linked list consists of nodes where each node contains a data field and a reference(link) to the next node in the list.

 class Node:
    def __init__(self, val, next=None):
        self.val = val
        self.next = next

class LinkedList:
    head = None

    def add(self, val):
        node = Node(val)
        if self.head is None:
            self.head = node
            return
        current_node = self.head
        while current_node.next is not None:
            current_node = current_node.next
        current_node.next = node

    def show(self):
        current_node = self.head
        while current_node is not None:
            print(current_node.val)
            current_node = current_node.next

    def pop(self):
        current_node = self.head
        if current_node is None:
            raise Exception("LinkedList is empty")
        if current_node.next is None:
            self.head = None
            return
        while current_node.next.next is not None:
            current_node = current_node.next
        current_node.next = None

    def delete_at(self, pos):
        current_node = self.head
        count = 1
        if current_node is None:
            raise Exception("LinkedList is empty")
        if pos == 1:
            self.head = current_node.next
        while count < pos-1:
            if current_node.next is None:
                raise Exception("LinkedList index out of bound")
            current_node = current_node.next
            count += 1
        current_node.next = current_node.next.next

    def add_at(self, pos, val):
        node = Node(val)
        current_node = self.head
        count = 1
        if current_node is None and pos == 1:
            self.head = node
            return
        elif current_node is None:
            raise Exception("LinkedList is empty. Try to give position as 1.")
        if pos == 1:
            node.next = self.head
            self.head = node
            return
        while count < pos-1:
            if current_node.next is None:
                raise Exception("LinkedList index out of bound")
            current_node = current_node.next
            count += 1
        node.next = current_node.next
        current_node.next = node



ll = LinkedList()
ll.add(1)
# ll.add(2)
# ll.add(3)
# ll.add(4)
# ll.add(5)
# ll.show()
# ll.pop()
# ll.show()
# ll.delete_at(100)
ll.add_at(1,10)
ll.show()