Doubly_Connected_Linked_Lists.ipynb

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    "\n",
    "class DoublyLinkedList():\n",
    "    def __init__(self, head = None, tail = None):\n",
    "        self.head = head\n",
    "        self.tail = tail\n",
    "\n",
    "        \n",
    "    def add_node_to_head(self, cargo):\n",
    "        node = Node(cargo)\n",
    "        if self.head == None:\n",
    "            self.head = node\n",
    "            self.tail = node\n",
    "            return\n",
    "        node.next = self.head\n",
    "        self.head.prev = node \n",
    "        self.head = node\n",
    "        \n",
    "        \n",
    "    def add_node_to_tail(self, cargo):\n",
    "        node = Node(cargo)\n",
    "        if self.head == None:\n",
    "            self.head = node\n",
    "            self.tail = node\n",
    "            return\n",
    "        key_node = self.head\n",
    "        while key_node.next != None:\n",
    "            key_node = key_node.next\n",
    "        key_node.next = node\n",
    "        node.prev = key_node\n",
    "        self.tail = node\n",
    "\n",
    "        \n",
    "    def length(self):\n",
    "        counter = 0\n",
    "        key_node = self.head\n",
    "        while key_node != None:\n",
    "            key_node = key_node.next\n",
    "            counter += 1\n",
    "        return counter\n",
    "    \n",
    "    \n",
    "    def length_count_from_tail(self):\n",
    "        counter = 0\n",
    "        key_node = self.tail\n",
    "        while key_node != None:\n",
    "            print(key_node.cargo)\n",
    "            key_node = key_node.prev\n",
    "            counter += 1\n",
    "        return counter\n",
    "    \n",
    "    \n",
    "    def peek_at_tail(self):\n",
    "        return self.tail.cargo\n",
    "\n",
    "    \n",
    "    def peek_at_head(self):\n",
    "        return self.head.cargo\n",
    "        \n",
    "    \n",
    "    def print_nodes(self):\n",
    "        if self.head == None: return None\n",
    "        key_node = self.head\n",
    "        while key_node != None:\n",
    "            print(key_node.cargo)\n",
    "            key_node = key_node.next\n",
    "         \n",
    "        \n",
    "    def reverse_print(self):\n",
    "        if self.tail == None: return None\n",
    "        key_node = self.tail\n",
    "        while key_node != None:\n",
    "            print(key_node.cargo)\n",
    "            key_node = key_node.prev\n",
    "            \n",
    "        \n",
    "    def reverse_print_recursively(self):\n",
    "        # create a new list\n",
    "        if self.head == None: return None\n",
    "        new_list = DoublyLinkedList()\n",
    "        new_list.head = self.head.next\n",
    "        new_list.reverse_print_recursively()\n",
    "        print(self.head.cargo)\n",
    "    \n",
    "    \n",
    "    def print_recursively(self):\n",
    "        if self.tail == None: return\n",
    "        new_list = DoublyLinkedList()\n",
    "        new_list.tail = self.tail.prev\n",
    "        new_list.print_recursively()\n",
    "        print(self.tail.cargo)\n",
    "        \n",
    "    \n",
    "    def delete_nth_index(self, n):\n",
    "        length = self.length()\n",
    "        if n >= length: return \n",
    "        if self.head == None: return \n",
    "        if n == 0:\n",
    "            self.head = self.head.next\n",
    "            self.head.prev = None\n",
    "            return\n",
    "        if (n+1) == length:\n",
    "            self.tail = self.tail.prev\n",
    "            self.tail.next = None\n",
    "            return\n",
    "        key_node = self.head\n",
    "        next_of_key_node = key_node.next\n",
    "        counter = 1\n",
    "        while next_of_key_node.next != None:\n",
    "            if counter == n:\n",
    "                key_node.next = next_of_key_node.next\n",
    "                next_of_key_node.next.prev = key_node\n",
    "                return\n",
    "            next_of_key_node = next_of_key_node.next\n",
    "            key_node = key_node.next\n",
    "            counter += 1\n",
    "        \n",
    "            \n",
    "    def remove_cargo_close_to_tail(self, cargo):\n",
    "        # there might be nodes with same cargo. Remove the cargo close to tail then end the search\n",
    "        if self.tail == None: return\n",
    "        if self.tail.cargo == cargo:\n",
    "            self.tail = self.tail.prev \n",
    "            self.tail.next = None\n",
    "        key_node = self.tail\n",
    "        prev_key_node = self.tail.prev\n",
    "        length = my_doubly_linked_list.length()\n",
    "        counter = 1\n",
    "        while prev_key_node != None:\n",
    "            if prev_key_node.cargo == cargo:\n",
    "                print('this item is removed: ', prev_key_node.cargo)\n",
    "                key_node.prev = prev_key_node.prev\n",
    "                prev_key_node.prev.next = key_node\n",
    "                return\n",
    "            key_node = key_node.prev\n",
    "            prev_key_node = prev_key_node.prev\n",
    "    \n",
    "    \n",
    "    def print_the_nth_node_from_head(self, n):\n",
    "        length = self.length()\n",
    "        if n > length: return None\n",
    "        if self.head == None: return None\n",
    "        key_node = self.head\n",
    "        counter = 1\n",
    "        while key_node != None:\n",
    "            if counter == n:\n",
    "                print(key_node.cargo)\n",
    "            key_node = key_node.next\n",
    "            counter += 1\n",
    "        \n",
    "    \n",
    "    def remove_the_last_node(self):\n",
    "        if self.head == None: return\n",
    "        key_node = self.head\n",
    "        if key_node.next == None:\n",
    "            self.head = None\n",
    "            self.tail = None\n",
    "        self.tail = self.tail.prev  \n",
    "        self.tail.next = None\n",
    "        \n",
    "    \n",
    "        \n",
    "    def reverse_the_doubly_linked_list(self):\n",
    "        new_list = DoublyLinkedList()\n",
    "        if self.head == None: return\n",
    "        key_node = self.head\n",
    "        while key_node != None:\n",
    "            new_list.add_node_to_head(key_node.cargo)\n",
    "            key_node = key_node.next\n",
    "        new_list.print_nodes()\n",
    "        \n",
    "        \n",
    "        \n",
    "        \n",
    "    \n",
    "    \n",
    "class Node():\n",
    "    def __init__(self, cargo, prev = None, next = None):\n",
    "        self.cargo = cargo\n",
    "        self.prev = prev\n",
    "        self.next = next\n",
    "        \n",
    "        \n",
    "        \n",
    "my_doubly_linked_list = DoublyLinkedList()\n",
    "# my_doubly_linked_list.add_node_to_tail(2)\n",
    "# my_doubly_linked_list.add_node_to_head(1)\n",
    "# my_doubly_linked_list.add_node_to_head(2)\n",
    "# my_doubly_linked_list.add_node_to_tail(3)\n",
    "# my_doubly_linked_list.add_node_to_head(0)\n",
    "my_doubly_linked_list.print_nodes() "
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