return kth to last element in a singly linked list

Author: nickolasteixeira

Python/chapter02/2.2 - Return Kth to Last/Nick.py

@@ -0,0 +1,105 @@
+#!/usr/bin/python3
+'''
+Return Kth to Last: Implement an algorithm to
+find the kth to last element of a singly linked list.
+'''
+import unittest
+
+
+class Node:
+    def __init__(self, data, next=None):
+        self.data = data
+        self.next = next
+
+    def __str__(self):
+        return str(self.data)
+
+
+class SinglyLinkedList:
+
+    def __init__(self):
+        self.head = None
+        self.size = 0
+
+    def insertHead(self, data):
+        print('Inserting head!----->', data)
+        n = Node(data)
+        temp = self.head
+        self.head = n
+        self.head.next = temp
+
+    def addNode(self, data):
+        if not self.head:
+            n = Node(data)
+            print('New Head added ---->', data)
+            self.head = n
+        else:
+            n = self.head
+            while (n.next):
+                n = n.next
+
+            print('New Node added ---->', data)
+            new_node = Node(data)
+            n.next = new_node
+
+    def kthToLastElement(self, num):
+        if num < 1:
+            print('Must be a positive number')
+            return
+
+        length = 0
+        temp = self.head
+        while temp:
+            length += 1
+            temp = temp.next
+
+        if num > length:
+            print('Input number cannot be larger than number of nodes')
+        else:
+            temp = self.head
+            for x in range(length - num):
+                temp = temp.next
+
+            print("{}th to last element --->".format(num), temp.data)
+
+    def printList(self):
+        n = self.head
+
+        print('Printing Singly Linked List')
+        while(n):
+            print(n)
+            n = n.next
+
+
+class Test(unittest.TestCase):
+    @classmethod
+    def setUpClass(cls):
+        cls.link = SinglyLinkedList()
+        cls.link.addNode(-1)
+        cls.link.addNode(-1)
+        cls.link.addNode(4)
+        cls.link.addNode(3)
+        cls.link.addNode(4)
+        cls.link.addNode(1)
+        cls.link.addNode(20)
+        cls.link.addNode(4)
+        cls.link.addNode(4)
+
+    @classmethod
+    def tearDownClass(cls):
+        print('---Teardown successful---')
+
+    def test1(self):
+        self.link.printList()
+
+    def test2(self):
+        self.link.kthToLastElement(0)
+        self.link.kthToLastElement(1)
+        self.link.kthToLastElement(2)
+        self.link.kthToLastElement(3)
+        self.link.kthToLastElement(9)
+        self.link.kthToLastElement(10)
+
+
+if __name__ == "__main__":
+    unittest.main()