python-dsa

recursion.py

@@ -0,0 +1,131 @@
+##single list 
+class Node:
+    def __init__(self,value=None):
+        self.value=value
+        self.next=None
+
+
+class SSLinked:
+    def __init__(self):
+        self.head=None
+        self.tail=None
+
+    def __iter__(self):
+        node=self.head
+        while node:
+            yield node
+            node=node.next
+
+    def insertssl(self,value,location):
+        newnode=Node(value)
+        if self.head is None:
+            self.head=newnode
+            self.tail=newnode
+
+        else:
+            #Fist we put the new node reference value as initial head value by using 
+            #newnode.next=self.head
+            #now we self.head reference to newnode
+            #
+            if location==0:
+                newnode.next=self.head
+                self.head=newnode
+#In the below sentences refer the algorithm as it says 1)-1 means we end up on the last node 
+#First delete the reference of the last node by newnode.next=None
+#now update inittially existing tail reference to the newnode
+#now make the new node as the tail 
+
+            elif location ==-1:
+                newnode.next=None
+                self.tail.next=newnode 
+                self.tail=newnode
+
+            else:
+                value=0
+                temp=self.head
+                while value<location-1:
+                    temp=temp.next
+                    index+=1
+
+                #
+                #
+                #first get tem and change its reference to the new node value ie temp.next=newnode
+                #then newnode.next=temp.next but use it in a variable
+                lastone=temp.next
+                temp.next=newnode
+                newnode.next=lastone
+                #if the temp is the last one then select the tail as the new node
+                if temp==self.tail:
+                    self.tail=newnode
+
+    def transversal(self):
+        node=self.head
+        while node is not None:
+            print(node.value)
+            node=node.next
+
+    def search(self,value):
+        node=self.head
+        while node is not None:
+            if node.value==value:
+                return node.value,"has been found"
+            node=node.next
+
+    def delete(self,location):
+        if self.head==None:
+            print("node does not exist")
+
+        else:
+            if location==0:
+                if self.head==self.tail:
+                    self.head=None
+                    self.tail=None
+
+                else:
+                    self.head=self.head.next
+
+            elif location ==-1:
+                if location==0:
+                    if self.head==self.tail:
+                        self.head=None
+                        self.tail=None
+
+                else:
+                    node=self.head
+                    while node is not None:
+                        if node.next==self.tail:
+                            break
+                        node=node.next
+                    node.next=None
+                    self.tail=node
+
+            else:
+                tempnode=self.head
+                index=0
+                while index<location-1:
+                    tempnode=tempnode.next
+                    index+=1
+
+                lastnode=tempnode.next
+                tempnode.next=lastnode.next
+
+    def deleteall(self):
+        self.head=None
+        self.tail=None
+
+
+
+singlelist=SSLinked()
+singlelist.insertssl(1,1)
+singlelist.insertssl(2,-1)
+singlelist.insertssl(3,-1)
+singlelist.insertssl(4,-1)
+singlelist.transversal()
+print(singlelist.search(2))
+singlelist.delete(2)
+singlelist.deleteall()
+print([n.value for n in singlelist ])
+
+
+
+