Merge pull request #212

Author: behrtam

config.json

@@ -417,6 +417,12 @@
       "difficulty": 1,
       "topics": [
       ]
+    },
+    {
+      "slug": "linked-list",
+      "difficulty": 1,
+      "topics": [
+      ]
     }
   ],
   "deprecated": [

exercises/linked-list/example.py

@@ -0,0 +1,47 @@
+class Node(object):
+    def __init__(self, value, next=None, prev=None):
+        self.value = value
+        self.next = next
+        self.prev = prev
+
+
+class LinkedList(object):
+    def __init__(self):
+        self.head = None
+        self.tail = None
+
+    def push(self, value):
+        new_node = Node(value)
+        if not self.head:
+            self.head = self.tail = new_node
+        else:
+            new_node.prev = self.tail
+            self.tail.next = new_node
+            self.tail = new_node
+
+    def pop(self):
+        node = self.tail
+        if node is None or node.prev is None:
+            self.head = self.tail = None
+        else:
+            self.tail = self.tail.prev
+            self.tail.next = None
+        return node.value
+
+    def shift(self):
+        node = self.head
+        if node is None or node.next is None:
+            self.head = self.tail = None
+        else:
+            self.head = self.head.next
+            self.head.prev = None
+        return node.value
+
+    def unshift(self, value):
+        new_node = Node(value)
+        if not self.head:
+            self.head = self.tail = new_node
+        else:
+            new_node.next = self.head
+            self.head.prev = new_node
+            self.head = new_node

exercises/linked-list/linked_list.py

@@ -0,0 +1,13 @@
+# Skeleton file for the Python "linked-list" exercise.
+
+
+class Node(object):
+    def __init__(self, value, next=None, prev=None):
+        self.value = value
+        self.next = next
+        self.prev = prev
+
+
+class LinkedList(object):
+    def __init__(self):
+        pass  # Complete the Deque class ...

exercises/linked-list/linked_list_test.py

@@ -0,0 +1,49 @@
+import unittest
+
+from linked_list import LinkedList
+
+
+class LinkedListTests(unittest.TestCase):
+
+    def setUp(self):
+        self.list = LinkedList()
+
+    def test_push_pop(self):
+        self.list.push(10)
+        self.list.push(20)
+        self.assertEqual(20, self.list.pop())
+        self.assertEqual(10, self.list.pop())
+
+    def test_push_shift(self):
+        self.list.push(10)
+        self.list.push(20)
+        self.assertEqual(10, self.list.shift())
+        self.assertEqual(20, self.list.shift())
+
+    def test_unshift_shift(self):
+        self.list.unshift(10)
+        self.list.unshift(20)
+        self.assertEqual(20, self.list.shift())
+        self.assertEqual(10, self.list.shift())
+
+    def test_unshift_pop(self):
+        self.list.unshift(10)
+        self.list.unshift(20)
+        self.assertEqual(10, self.list.pop())
+        self.assertEqual(20, self.list.pop())
+
+    def test_all(self):
+        self.list.push(10)
+        self.list.push(20)
+        self.assertEqual(20, self.list.pop())
+        self.list.push(30)
+        self.assertEqual(10, self.list.shift())
+        self.list.unshift(40)
+        self.list.push(50)
+        self.assertEqual(40, self.list.shift())
+        self.assertEqual(50, self.list.pop())
+        self.assertEqual(30, self.list.shift())
+
+
+if __name__ == '__main__':
+    unittest.main()