সিঙ্গলি লিংকড লিস্ট #

class Node():
    """
    @description: This class will act as node for Linked List and will hold data.
    @params:
        item: item means data item
        next_node: a pointer, indicates the address of next node
    """

    def __init__(self, item=None, next_node=None):
        self.item = item
        self.next_node = next_node


class SinglyLinkedList():
    """
    @description: This class defines several methods for Singly Linked List.
    @params:
        head: indicates the first node of list
    """

    def __init__(self, head=None):
        self.head = head

    def appendleft(self, item):
        # adds an item to the head of the list
        new_node = Node(item)
        new_node.next_node = self.head
        self.head = new_node

    def append(self, item):
        # adds an item to the end of the list
        current = self.head
        if current:
            while current.next_node:
                current = current.next_node
            current.next_node = Node(item)
        else:
            self.head = Node(item)

    def insert(self, position, item):
        # adds an item to an exact position of the list
        if position == 0:
            self.appendleft(item)
            print(item, "inserted to position", position)
        elif position == self.size():
            self.append(item)
            print(item, "inserted to position", position)
        elif position > self.size():
            print("Index out of range")
        else:
            current = self.head
            index = 0
            while current:
                if index != position:
                    previous = current
                    current = current.next_node
                    index += 1
                else:
                    new_node = Node(item, current)
                    previous.next_node = new_node
                    current = False
                    print(item, "inserted to position", position)

    def is_empty(self):
        # checks whether the list is empty or not
        if self.head == None:
            return True
        else:
            return False

    def size(self):
        # returns the total items number of the list
        current = self.head
        count = 0
        while current:
            count += 1
            current = current.next_node
        return count

    def index(self, item):
        # returns the index position of an item in the list
        current = self.head
        index = 0
        while current:
            if current.item == item:
                return index
            else:
                current = current.next_node
                index += 1
        return None

    def search(self, item):
        # checks whether an item exist in the list or not
        current = self.head
        found = False
        while current and not found:
            if current.item == item:
                found = True
            else:
                current = current.next_node
        if current is None:
            print("Item not found")
        return found

    def popleft(self):
        # removes the first item of the list
        if self.is_empty():
            print("Empty list")
        else:
            current = self.head
            temp = current.item
            self.head = current.next_node
            del current
            return temp

    def pop(self):
        # removes the last item of the list
        if self.is_empty():
            print("Empty list")
        else:
            current = self.head
            previous = None
            while current.next_node:
                previous = current
                current = current.next_node
            if current == self.head:
                self.head = None
            else:
                previous.next_node = None
            temp = current.item
            del current
            return temp

    def remove(self, item):
        # removes an item from the listot
        if self.is_empty():
            print("Empty list")
        else:
            current = self.head
            previous = None
            found = False
            while current and not found:
                if current.item == item:
                    found = True
                else:
                    previous = current
                    current = current.next_node
            if current is None:
                print("Item not found")
            elif previous is None:
                self.popleft()
                print(item, "removed")
            else:
                temp = current.next_node
                del current
                print(item, "removed")
                previous.next_node = temp

    def printlist(self):
        if self.is_empty():
            print("Empty list")
        else:
            current = self.head
            print(current.item)
            while current.next_node:
                current = current.next_node
                print(current.item)

def main():
    # defining the main function for the singly linked list
    mylist = SinglyLinkedList()
    # mylist is an object of SinglyLinkedList class
    while True:
        print("1. Append to Left \n2. Append \n3. Insert \n4. Get Size \n5. Search \n6. Get Index \n7. Remove \n8. Pop from Left \n9. Pop \n10. Print List \n11. Quit")
        print("\nWhat do you wanna do now?")
        case = int(input())
        # starting something, equivalent to Switch statement in C/C++
        if case == 1:
            # in this case, we will call our appendleft method
            print("Input item, you wanna append to left of list:")
            item = input()
            mylist.appendleft(item)
            print("Congrats!", item, "has been added.")
        elif case == 2:
            # in this case, we will call our appendleft method
            print("Input item, you wanna append to list:")
            item = input()
            mylist.append(item)
            print("Congrats!", item, "has been appended.")
        elif case == 3:
            # in this case, we will call our appendleft method
            print("Input position:")
            position = int(input())
            print("Input item, you wanna push to list:")
            item = input()
            mylist.insert(position, item)
        elif case == 4:
            # in this case, we will call our size method
            print("There are", mylist.size(), "items in the list.")
        elif case == 5:
            # in this case, we will call our search method
            print("Input item, you wanna search in list:")
            item = input()
            print(mylist.search(item))
        elif case == 6:
            # in this case, we will call our insert method
            print("Input item, you wanna know its index:")
            item = input()
            index = mylist.index(item)
            print(item, "is in index number", index)
        elif case == 7:
            # in this case, we will call our remove method
            if mylist.is_empty():
                print("Empty list")
            else:
                print("Input item, you wanna remove:")
                item = input()
                mylist.remove(item)
        elif case == 8:
            # in this case, we will call our pop method without position
            if mylist.is_empty():
                print("Empty list")
            else:
                item = mylist.popleft()
                print(item, "removed")
        elif case == 9:
            # in this case, we will call our pop method without position
            if mylist.is_empty():
                print("Empty list")
            else:
                item = mylist.pop()
                print(item, "removed")
        elif case == 10:
            # in this case, we will print our list
            if mylist.is_empty():
                print("Empty list")
            else:
                mylist.printlist()
        elif case == 11:
            # in this case, we will quit our script
            print("The script is gonna quit.")
            quit()
        else:
            print("Oops! Wrong Choice.")
            main()

if __name__ == '__main__':
    main()