Create reverse_linked_list.py

Author: learning-zone

reverse_linked_list.py

@@ -0,0 +1,68 @@
+class Node(object):
+    """ Class in a linked list. """
+
+    def __init__(self, data, next=None):
+        self.data = data
+        self.next = next
+
+    def as_string(self):
+        """Represent data for this node and it's successors as a string.
+
+        >>> Node(3).as_string()
+        '3'
+
+        >>> Node(3, Node(2, Node(1))).as_string()
+        '321'
+        """
+
+        out = []
+        n = self
+
+        while n:
+            out.append(str(n.data))
+            n = n.next
+
+        return ''.join(out)
+
+
+def reverse_linked_list(head):
+    """Given singly linked list head node, return head node of new, reversed linked list.
+
+    >>> ll = Node(1, Node(2, Node(3)))
+    >>> reverse_linked_list(ll).as_string()
+    '321'
+
+    >>> ll = Node(1, Node(2, Node(3)))
+    >>> new_ll = reverse_linked_list(ll)
+    >>> new_ll.as_string()
+    '321'
+    """
+
+    prev = None
+    curr = head
+
+    while curr:
+        next = curr.next
+        curr.next = prev
+        prev = curr
+        curr = next
+
+
+    return prev
+
+
+
+
+
+
+
+
+
+
+
+if __name__ == '__main__':
+    import doctest
+    results = doctest.testmod()
+
+    if results.failed == 0:
+        print "ALL TESTS PASSED!"