update double linked list

Author: HSanny

data_structures/3_LinkedList/double_linked_list.py

@@ -0,0 +1,107 @@
+class Node:
+    def __init__(self, prev=None, data=None, next=None):
+        self.prev = prev
+        self.data = data
+        self.next = next
+
+
+class DoubleLinkedList:
+    def __init__(self):
+        self.head = None  # prev, data, next = None
+
+    def print_forward(self):
+        if self.head is None:
+            raise Exception("The linked list is empty")
+
+        current_node = self.head
+        ll_str = ""
+        while current_node:
+            ll_str += str(current_node.data) + '-->' + str(current_node.next.data) if current_node.next else None
+            current_node = current_node.next
+        print(ll_str)
+    def print_backward(self):
+        if self.head is None:
+            raise Exception("The linked list is empty")
+        current_node = self.head
+        ll_str = ""
+        while current_node:
+            if current_node.next:
+                ll_str += str(current_node.next.data) + str(current_node.data)
+            else:
+                ll_str += "" + str(current_node.data)
+            current_node = current_node.next
+        print(ll_str)
+
+    def get_last_node(self):
+        if self.head is None:
+            raise Exception("The list is empty!!")
+        current_node = self.head
+        while current_node:
+            if current_node.next is None:
+                return current_node
+            current_node = current_node.next
+
+    def get_length(self):
+        count = 0
+        current_node = self.head
+        while current_node:
+            count += 1
+            current_node = current_node.next
+        return count
+
+    def insert_at_beginning(self, data):
+        if self.head is None:
+            self.head = Node(None, data, None)
+            return
+        new_node = Node(None, data, next=self.head)
+        self.head = new_node
+
+    def insert_at_end(self, data):
+        if self.head is None:
+            self.head = Node(None, data, None)
+            return
+        current_node = self.head
+        while current_node:
+            if not current_node.next:
+                new_node = Node(current_node, data, next=None)
+                current_node.next = new_node
+                return
+            current_node = current_node.next
+
+    def insert_at(self, index, data):
+        if index < 0 or index > self.get_length():
+            raise Exception("Invalid index had been given !!")
+        if self.head is None:
+            if index == 0:
+                self.head = Node(None, data, None)
+                return
+            else:
+                raise Exception("The list is empty")
+        curr_ind = 0
+        curr_node = self.head
+        while curr_node:
+            if curr_ind == index - 1:
+                new_node = Node(curr_node.next, data, curr_node.next.prev)
+                curr_node.next = new_node
+                return
+            curr_node = curr_node.next
+    def remove_at(self, index):
+        return
+
+    def insert_values(self, data_list):
+        return
+
+
+if __name__ == '__main__':
+    ll = DoubleLinkedList()
+    ll.insert_values(["banana", "mango", "grapes", "orange"])
+    ll.print_forward()
+    ll.print_backward()
+    ll.insert_at_end("figs")
+    ll.print_forward()
+    ll.insert_at(0, "jackfruit")
+    ll.print_forward()
+    ll.insert_at(6, "dates")
+    ll.print_forward()
+    ll.insert_at(2, "kiwi")
+    ll.print_forward()

data_structures/3_LinkedList/linked_list.py

@@ -23,10 +23,10 @@ def print(self):
     def get_length(self):
         count = 0
         current_node = self.head
-        if current_node:
+        while current_node:
             count += 1
             current_node = current_node.next
-        print("Length of the linked list: ", count)
+        # print("Length of the linked list: ", count)
         return count
 
     def insert_at_beginning(self, data):
@@ -60,6 +60,7 @@ def insert_at(self, index, data):
             curr_count += 1
 
     def remove_at(self, index):
+
         if index < 0 or index >= self.get_length():
             raise Exception("Invalid index been given!")
 
@@ -81,14 +82,62 @@ def insert_values(self, data_list):
         for data in data_list:
             self.insert_at_end(data)
 
+    def insert_after_value(self, data_after, data_to_insert):
+        # search for first occurrence of data_after
+        # insert data_to_insert after data_after
+        if self.head is None:
+            raise Exception("The list is empty!")
+        current_node = self.head
+        while current_node:
+            if str(current_node.data) == str(data_after):
+                new_node = Node(data_to_insert, current_node.next)
+                current_node.next = new_node
+            current_node = current_node.next
+
+    def remove_by_value(self, data):
+        # remove first node that contains data
+        if self.head is None:
+            raise Exception("The list is empty!")
+
+        if self.head.data == data:
+            self.head = self.head.next
+            return
+        current_node = self.head
+        while current_node.next:
+            if current_node.next.data == data:
+                current_node.next = current_node.next.next
+                return
+            current_node = current_node.next
+        print("value given is not in the linked list")
 
 if __name__ == '__main__':
+    # ll = SinglyLinkedList()
+    # ll.insert_values(["banana", "mango", "grapes", "orange"])
+    # ll.print()
+    # ll.insert_at(1, "blueberry")
+    # ll.print()
+    # ll.remove_at(2)
+    # ll.print()
+    #
+    # ll.insert_values([45, 7, 12, 567, 99])
+    # ll.print()
+    # ll.insert_at_end(67)
+    # ll.print()
+
     ll = SinglyLinkedList()
     ll.insert_values(["banana", "mango", "grapes", "orange"])
-    ll.insert_at(1, "blueberry")
-    ll.remove_at(2)
     ll.print()
-
-    ll.insert_values([45, 7, 12, 567, 99])
-    ll.insert_at_end(67)
+    ll.insert_after_value("mango", "apple")  # insert apple after mango
+    ll.print()
+    ll.remove_by_value("orange")  # remove orange from linked list
+    ll.print()
+    ll.remove_by_value("figs")
+    ll.print()
+    ll.remove_by_value("banana")
+    ll.print()
+    ll.remove_by_value("mango")
+    ll.print()
+    ll.remove_by_value("apple")
     ll.print()
+    ll.remove_by_value("grapes")
+    ll.print()