Merging linked lists in Python

Author: Deepali-Srivastava

linked-list/merging-linked-lists.py

@@ -0,0 +1,159 @@
+# Copyright (C) Deepali Srivastava - All Rights Reserved
+# This code is part of DSA course available on CourseGalaxy.com  
+
+class Node:
+
+    def __init__(self,value):
+        self.info = value 
+        self.link = None 
+        
+
+class SingleLinkedList:
+
+    def __init__(self):
+        self.start = None
+    
+    def display_list(self):
+        if self.start is None:
+            print("List is empty")
+            return
+        else:
+            print("List is :   ")
+            p = self.start 
+            while p is not None:
+                print(p.info , " ", end='')
+                p = p.link 
+            print()
+   
+    def insert_at_end(self, data):
+        temp = Node(data)
+        if self.start is None:
+            self.start = temp
+            return
+        
+        p = self.start
+        while p.link is not None:
+            p = p.link
+        p.link = temp
+
+
+    def create_list(self):
+        n = int(input("Enter the number of nodes : "))
+        if n == 0:
+            return
+        for i in range(n):
+            data = int(input("Enter the element to be inserted : "))
+            self.insert_at_end(data)
+    
+
+    def bubble_sort_exdata(self):
+        end = None
+        while end != self.start.link:
+
+            p = self.start
+            while  p.link != end:
+                q = p.link 
+                if p.info > q.info:
+                    p.info,q.info = q.info,p.info 
+                p = p.link     
+            end = p
+
+    def merge1(self, list2):
+        merge_list = SingleLinkedList()
+        merge_list.start = self._merge1(self.start, list2.start)
+        return merge_list
+    
+    def _merge1(self, p1, p2):
+        if p1.info <= p2.info:
+            startM = Node(p1.info)
+            p1 = p1.link
+        else:
+            startM = Node(p2.info)
+            p2 = p2.link;
+        
+        pM = startM
+
+        while p1 is not None and p2 is not None:
+            if p1.info <= p2.info :
+                pM.link = Node(p1.info)
+                p1 = p1.link
+            else:
+                pM.link = Node(p2.info);
+                p2 = p2.link;
+            pM = pM.link;
+            
+
+        #If second list has finished and elements left in first list
+        while p1 is not None:
+            pM.link = Node(p1.info)
+            p1 = p1.link
+            pM = pM.link
+        
+        #If first list has finished and elements left in second list
+        while p2 is not None:
+            pM.link = Node(p2.info)
+            p2 = p2.link
+            pM = pM.link
+
+        return startM
+
+        
+    def merge2(self,list2):
+        merge_list = SingleLinkedList()
+        merge_list.start = self._merge2(self.start, list2.start)
+        return merge_list
+        
+    def _merge2(self, p1, p2):
+
+        if p1.info <= p2.info:
+            startM = p1
+            p1 = p1.link
+        else:
+            startM = p2
+            p2 = p2.link
+            
+        pM = startM
+
+        while p1 is not None and p2 is not None:
+            if p1.info <= p2.info :
+                pM.link = p1
+                pM = pM.link
+                p1 = p1.link
+            else:
+                pM.link = p2
+                pM = pM.link
+                p2 = p2.link
+            
+        if p1 is None:
+            pM.link = p2
+        else:
+            pM.link = p1
+
+        return startM
+        
+
+#########################################################################################
+
+list1 = SingleLinkedList()
+list2 = SingleLinkedList()
+
+list1.create_list() 
+list2.create_list()
+
+list1.bubble_sort_exdata()
+list2.bubble_sort_exdata()
+	
+print("First List - "); list1.display_list()
+print("Second List - "); list2.display_list()
+
+list3 = list1.merge1(list2)
+print("Merged List - "); list3.display_list()
+		
+print("First List - "); list1.display_list()
+print("Second List - "); list2.display_list()
+		
+list3 = list1.merge2(list2)
+print("Merged List - "); list3.display_list()
+print("First List - ");  list1.display_list()
+print("Second List - "); list2.display_list()
+