finished 2.2

Author: camilosalazar98

Python/chapter02/2.2 - Return Kth to Last/camilo_solution_2.2.py

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+"""
+Return Kth to Last: Implement an algorithm to find the kth to last element of
+a singly linked list.
+Hints:#8, #25, #41, #67, #126
+"""
+
+class Node:
+    #Singly link list
+    def __init__(self,data):
+        self.data = data
+        self.next = None
+
+class linklist:
+    #linkList class
+    def __init__(self):
+        self.head = None
+        self.size = 0
+
+    def push(self,data):
+        node = Node(data)# create a new node
+
+        if self.head == None: #check to see if the head node is empty
+            self.head = node # If its empty add it to the new node
+            self.size = 1
+            return
+        #if the head of the linklist is filled
+
+        current = self.head
+        while current.next is not None:#Check the current postion is empty
+        #Move to the next line if nothing is there
+            current = current.next
+
+
+        current.next = node #point self.head to a new node
+        self.size+=1
+
+
+
+
+    def lenght(self):
+        #note the count doesn't start at zero
+        cur = self.head
+        counter = 0
+        while cur is not None:
+            counter+=1
+            cur = cur.next
+        print('Linklist len: '+str(counter))
+        return counter
+
+    def printList(self):
+        curr = self.head
+        elem = []
+
+        while(curr != None):
+            elem.append(curr.data)
+            curr = curr.next
+        print(elem)
+    #1->2->3
+    def remove_node(self,data):
+        #1->2->3
+        curr = self.head
+        if curr is not None and curr.data == data:
+            self.head = curr.next
+            curr = None
+        #look for the node that has the data we are looking for
+        while curr is not None:
+            if curr.data == data:
+                break
+            prev = curr
+            curr = curr.next
+
+        #if data isn't found just reutrn
+        if(curr == None):
+            return
+
+        #allow us to unlink the nodes
+        prev.next = curr.next
+        curr = None
+
+    def Kth_to_Last(self,num):
+        counter = 1 # We need to keep track where we are
+        curr = self.head
+        goal = self.size - num# kth to last element
+        while curr is not None:
+            if goal == counter:
+                return curr.data
+            counter+=1
+            curr = curr.next
+
+
+
+
+
+
+llist = linklist()
+llist.push(1)
+llist.push(2)
+llist.push(3)
+llist.push(4)
+llist.push(5)
+llist.printList()
+
+llist.lenght()
+print(llist.Kth_to_Last(1))# should return 4
+print(llist.Kth_to_Last(2))# should return 4
+print(llist.Kth_to_Last(3))# should return 4