Correction during revising session with Kim

tree.py

@@ -3,7 +3,6 @@
 
 import sys
 
-
 class Node:
   def __init__(self, k):
     self.key = k
@@ -48,7 +47,14 @@ def reverse_walk(t):
 
 # Complexity (worst): Theta(n)
 def search(tree, k):
-  pass
+  if tree is None:
+    return None
+  elif tree.key == k:
+    return tree
+  elif k < tree.key:
+    return search(tree.left, k)
+  else:
+    return search(tree.right, k)
 
 
 # Complexity (worst): Theta(n)
@@ -92,13 +98,21 @@ def predecessor(t):
 
 
 def insert(t, k):
-  if t is None:
-    return Node(k)
-  if t.key < t.key:
-    t.set_left(insert(t.left, k))
+  insert_node(t, Node(k))
+
+
+def insert_node(t, node):
+  if node.key < t.key:
+    if t.left is None:
+      t.set_left(node)
     else:
-    tree.set_right(insert(t.right, k))
-  return t
+      insert_node(t.left, node)
+  else:
+    if t.right is None:
+      t.set_right(node)
+    else:
+      insert_node(t.right, node)
+
 
 def right_rotate(x):
   # assume x is not None
@@ -108,6 +122,7 @@ def right_rotate(x):
   t.right = x
   return t
 
+
 def left_rotate(x):
   # assume x is not None
   # assume x.right is not None
@@ -116,6 +131,7 @@ def left_rotate(x):
   t.left = x
   return t
 
+
 def root_insert(t, k):
   if t is None:
     return Node(k)
@@ -126,6 +142,36 @@ def root_insert(t, k):
     t.set_left(root_insert(t.left, k))
     return right_rotate(t)
 
+
+def unlink_me(node, to_link):
+  if node.parent == None:
+    node.key = to_link.key
+    node.left = to_link.left
+    node.right = to_link.right
+  elif node.parent.left == node:
+    node.parent.left = to_link
+  else:
+    node.parent.right = to_link
+
+
+def delete(t, k):
+  to_delete = search(t, k)
+  if to_delete is None:
+    return
+  elif to_delete.left is None:
+    unlink_me(to_delete, to_delete.right)
+  elif to_delete.right is None:
+    unlink_me(to_delete, to_delete.left)
+  else:
+    if abs(to_delete.left.key - to_delete.key) < abs(to_delete.right.key -
+        to_delete.key):
+      unlink_me(to_delete, to_delete.left)
+      insert_node(to_delete.left, to_delete.right)
+    else:
+      unlink_me(to_delete, to_delete.right)
+      insert_node(to_delete.right, to_delete.left)
+
+
 ###############################################################################
 # Code for printing trees, ignore this
 
@@ -196,15 +242,20 @@ def print_w(t, width):
 
 
 if __name__ == "__main__":
-  print_tree(tree)
-
-  in_order_walk(tree)
-  print()
-
-  reverse_walk(tree)
-  print()
-
-  print(tree.left.right.right.key)
-  print(successor(tree.left.right.right).key)
-  print(predecessor(tree.left.right.right).key)
+  args = [x for x in sys.argv[1:]]
+  T = Node(int(args[0]))
+  for i in range(1, len(args)):
+    if args[i] == '|':
+      break
+    print_tree(T)
+    print("\nInsert " + str(args[i]) + ":")
+    insert(T, int(args[i]))
+  for i in range(i+1, len(args)):
+    print_tree(T)
+    print("\nDelete " + str(args[i]) + ":")
+    delete(T, int(args[i]))
+  print_tree(T)
+  #print(tree.left.right.right.key)
+  #print(successor(tree.left.right.right).key)
+  #print(predecessor(tree.left.right.right).key)