singly linked list

Linked-Lists/linkedlist.py

@@ -0,0 +1,147 @@
+#!python
+
+from __future__ import print_function
+
+
+class Node(object):
+
+    def __init__(self, data):
+        """Initialize this node with the given data"""
+        self.data = data
+        self.next = None
+
+    def __repr__(self):
+        """Return a string representation of this node"""
+        return 'Node({})'.format(repr(self.data))
+
+
+class LinkedList(object):
+
+    def __init__(self, iterable=None):
+        """Initialize this linked list; append the given items, if any"""
+        self.head = None
+        self.tail = None
+        if iterable:
+            for item in iterable:
+                self.append(item)
+
+    def __repr__(self):
+        """Return a string representation of this linked list"""
+        return 'LinkedList({})'.format(self.as_list())
+
+    def as_list(self):
+        """Return a list of all items in this linked list"""
+        result = []
+        current = self.head
+        while current is not None:
+            result.append(current.data)
+            # result.append(current)
+            current = current.next
+        return result
+
+    def is_empty(self):
+        """Return True if this linked list is empty, or False"""
+        return self.head is None
+
+    def length(self):
+        """Return the length of this linked list by traversing its nodes"""
+        count = 0
+        current = self.head
+        while current is not None:
+            count += 1
+            current = current.next
+        return count
+
+    def append(self, item):
+        """Insert the given item at the tail of this linked list"""
+        node = Node(item)
+        if self.tail is not None:
+            currentTailNode = self.tail
+            currentTailNode.next = node
+            self.tail = node
+        else:
+            self.head = node
+            self.tail = node
+
+    def prepend(self, item):
+        """Insert the given item at the head of this linked list"""
+        # TODO: prepend given item
+        node = Node(item)
+        if self.head is not None:
+            currentHeadNode = self.head
+            node.next = currentHeadNode
+            self.head = node
+        else: 
+            self.head = node
+            self.tail = node
+
+    def delete(self, item):
+        """Delete the given item from this linked list, or raise ValueError"""
+        current = self.head
+        try:
+            if current.data == item:
+                if current.data == self.tail.data:
+                    self.head = None
+                    self.tail = None
+                    return
+                else: 
+                    self.head = current.next
+                return None
+
+            while current.next is not None: 
+                if current.next.data == item:
+                    #remove item
+                    if current.next == self.tail:
+                        self.tail = current
+                        current.next = None
+                    else:
+                        current.next = current.next.next
+
+                    return 
+                else: 
+                    current = current.next
+        except AttributeError:
+            raise ValueError
+
+    def find(self, quality):
+        """Return an item from this linked list satisfying the given quality"""
+        # TODO: find item where quality(item) is True
+        current = self.head
+
+        try: 
+            while current.data is not None:
+                if quality(current.data) is True: 
+                    return current.data
+                else:
+                    current = current.next
+        except AttributeError:
+            return None
+
+
+
+def test_linked_list():
+    ll = LinkedList()
+    print(ll)
+    ll.append('A')
+    print(ll)
+    ll.append('B')
+    print(ll)
+    ll.append('C')
+    print(ll)
+    print('head: ' + str(ll.head))
+    print('tail: ' + str(ll.tail))
+    print(ll.length())
+
+    ll.delete('A')
+    print(ll)
+    ll.delete('C')
+    print(ll)
+    ll.delete('B')
+    print(ll)
+    print('head: ' + str(ll.head))
+    print('tail: ' + str(ll.tail))
+    print(ll.length())
+
+
+if __name__ == '__main__':
+    test_linked_list()