Q2.3 Delete middle node

cracking_the_code/chapter2/Q2.3_delete_middle_node.py

@@ -0,0 +1,24 @@
+import logging
+from linked_list import *
+
+
+# We can simply copy the value of next node to the current node and delete next node
+def delete_middle_node(node):
+    if not node:
+        return
+    node.value = node.next.value
+    node.next = node.next.next
+
+
+def main():
+    # build a list
+    lst = LinkedList(['a', 'b', 'c', 'd', 'e', 'f'])
+    p = lst.head()
+    while p.value != 'c':
+        p = p.next
+    delete_middle_node(p)
+    lst.print()
+
+
+if __name__ == '__main__':
+    main()

cracking_the_code/chapter2/linked_list.py

@@ -8,7 +8,7 @@ def __init__(self, v):
 
 
 class LinkedList:
-    head = None
+    _head = None
 
     def __init__(self, lst=None):
         if isinstance(lst, list):
@@ -20,8 +20,8 @@ def __eq__(self, other):
             return False
         if self.length() != other.length():
             return False
-        n = self.head
-        m = other.head
+        n = self._head
+        m = other._head
         while n:
             if n.value != m.value:
                 return False
@@ -30,18 +30,18 @@ def __eq__(self, other):
         return True
 
     def length(self):
-        n = self.head
+        n = self._head
         count = 0
         while n:
             count += 1
             n = n.next
 
     def add(self, v):
         new = Node(v)
-        if not self.head:
-            self.head = new
+        if not self._head:
+            self._head = new
             return
-        p = self.head
+        p = self._head
         while p.next:
             p = p.next
         p.next = new
@@ -51,11 +51,14 @@ def list_to_linkedlist(self, lst):
             self.add(item)
 
     def print(self):
-        p = self.head
+        p = self._head
         str_lst = ''
         if not p:
             print('[]')
         while p:
             str_lst += '{}->'.format(p.value)
             p = p.next
         print(str_lst)
+
+    def head(self):
+        return self._head