Merge pull request #105 from aarjavpatni/circular-linked-list

Circular Linked List

Author: BeeBombshell

DSA/circularLinkedList.py

@@ -0,0 +1,151 @@
+class Node:
+ def __init__(self, data):
+ self.data = data
+ self.next = None
+
+class CircularLinkedList:
+ def __init__(self):
+ self.last = None
+
+ def addToEmpty(self, data):
+
+ if self.last != None:
+ return self.last
+
+ # allocate memory to the new node and add data to the node
+ newNode = Node(data)
+
+ # assign last to newNode
+ self.last = newNode
+
+ # create link to iteself
+ self.last.next = self.last
+ return self.last
+
+ def addFront(self, data):
+
+ # check if the list is empty
+ if self.last == None:
+ return self.addToEmpty(data)
+
+ # allocate memory to the new node and add data to the node
+ newNode = Node(data)
+
+ # store the address of the current first node in the newNode
+ newNode.next = self.last.next
+
+ # make newNode as last
+ self.last.next = newNode
+
+ return self.last
+ 
+ def addEnd(self, data):
+ # check if the node is empty
+ if self.last == None:
+ return self.addToEmpty(data)
+
+ # allocate memory to the new node and add data to the node
+ newNode = Node(data)
+
+ # store the address of the last node to next of newNode
+ newNode.next = self.last.next
+
+ # point the current last node to the newNode
+ self.last.next = newNode
+
+ # make newNode as the last node
+ self.last = newNode
+
+ return self.last
+
+ def addAfter(self, data, item):
+
+ # check if the list is empty
+ if self.last == None:
+ return None
+
+ newNode = Node(data)
+ p = self.last.next
+ while p:
+
+ # if the item is found, place newNode after it
+ if p.data == item:
+
+ # make the next of the current node as the next of newNode
+ newNode.next = p.next
+
+ # put newNode to the next of p
+ p.next = newNode
+
+ if p == self.last:
+ self.last = newNode
+ return self.last
+ else:
+ return self.last
+ p = p.next
+ if p == self.last.next:
+ print(item, "The given node is not present in the list")
+ break
+ 
+ def deleteNode(self, last, key):
+
+ # If linked list is empty
+ if last == None:
+ return
+
+ # If the list contains only a single node
+ if (last).data == key and (last).next == last:
+
+ last = None
+
+ temp = last
+ d = None
+
+ # if last node is to be deleted
+ if (last).data == key:
+
+ # find the node before the last node
+ while temp.next != last:
+ temp = temp.next
+
+ # point temp node to the next of last i.e. first node
+ temp.next = (last).next
+ last = temp.next
+
+ # travel to the node to be deleted
+ while temp.next != last and temp.next.data != key:
+ temp = temp.next
+
+ # if node to be deleted was found
+ if temp.next.data == key:
+ d = temp.next
+ temp.next = d.next
+
+ return last
+
+ def traverse(self):
+ if self.last == None:
+ print("The list is empty")
+ return
+
+ newNode = self.last.next
+ while newNode:
+ print(newNode.data, end=" ")
+ newNode = newNode.next
+ if newNode == self.last.next:
+ break
+
+if __name__ == "__main__":
+
+ cll = CircularLinkedList()
+
+ last = cll.addToEmpty(6)
+ last = cll.addEnd(8)
+ last = cll.addFront(2)
+ last = cll.addAfter(10, 2)
+
+ cll.traverse()
+
+ last = cll.deleteNode(last, 8)
+ print()
+ cll.traverse()