delete middle node

Author: nickolasteixeira

Python/chapter02/2.3 - Delete Middle Node/Nick.py

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+#!/usr/bin/python3
+import unittest
+from random import randint
+'''
+Delete Middle Node: Implement an algorithm to delete a node in the middle (i.e., any node but the first and last node, not necessarily the exact middle) of a singly linked list, given only access to that node. EXAMPLE lnput:the node c from the linked lista->b->c->d->e->f Result: nothing is returned, but the new linked list looks like a->b->d->e->f Hints:#72
+'''
+
+'''
+Get clarification on this question:
+1. Will I always know that I will get a middle node? (non end or head node)
+2. What if the node is only 2 lengths long?
+3. What input will I get?
+'''
+
+
+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
+
+    def addNode(self, data):
+        # adds node to head if no head
+        node = Node(data)
+        if not self.head:
+            self.head = node
+        # adds to end of linked list
+        else:
+            temp = self.head
+            while temp.next:
+                temp = temp.next
+            temp.next = node
+
+    def printList(self):
+        if self.head is None:
+            print('Nothing to print')
+            return
+
+        temp = self.head
+        while temp:
+            print(temp.data)
+            temp = temp.next
+
+    def findSize(self):
+        if self.head is None:
+            print('Nothing to find the size of')
+            return
+
+        temp = self.head
+        count = 0
+        while temp:
+            count += 1
+            temp = temp.next
+        return count
+
+    def findMiddleNode(self):
+        size = self.findSize()
+        if size and size > 2:
+            # cannot be the size of the node (tail) or the first node (head)
+            temp = self.head
+            randomNum = randint(2, size - 1)
+            for x in range(1, randomNum):
+                temp = temp.next
+            return temp
+        else:
+            print("Not able to access a non head or tail node")
+            return None
+
+    def deleteMiddleNode(self, node):
+        '''The solution is simply to copy the data
+        from the next node over to the current node,
+        and then to delete the next node.
+        '''
+        if node is None:
+            print('No node to delete')
+            return
+
+        temp = node.next
+        node.data = temp.data
+        node.next = temp.next
+        del temp
+
+
+class Test(unittest.TestCase):
+
+    @classmethod
+    def setUpClass(cls):
+        cls.l = SinglyLinkedList()
+        cls.l.addNode(-1)
+        cls.l.addNode(3)
+        cls.l.addNode('hello')
+        cls.l.addNode(100)
+        cls.l.addNode(5)
+        cls.l.printList()
+
+    @classmethod
+    def tearDownClass(self):
+        pass
+
+    def test1(self):
+        numNodes = self.l.findSize()
+        print('Number of nodes {}'.format(numNodes))
+
+    def test2(self):
+        node = self.l.findMiddleNode()
+        print('Middle node -->', node.data)
+        print('Deleting middle node')
+        self.l.deleteMiddleNode(node)
+        self.l.printList()
+
+
+if __name__ == '__main__':
+    unittest.main()