adding lca advanced

Author: michaelcheng1991

problems/LCAII.py

@@ -0,0 +1,92 @@
+'''
+Given two nodes in a binary tree (with parent pointer available), find their lowest common ancestor.
+
+Assumptions
+
+There is parent pointer for the nodes in the binary tree
+
+The given two nodes are not guaranteed to be in the binary tree
+
+Examples
+
+        5
+
+      /   \
+
+     9     12
+
+   /  \      \
+
+  2    3      14
+
+The lowest common ancestor of 2 and 14 is 5
+
+The lowest common ancestor of 2 and 9 is 9
+
+The lowest common ancestor of 2 and 8 is null (8 is not in the tree)
+
+'''
+class BinaryTree:
+	def __init__(self, val):
+		self.val = val
+		self.left = None
+		self.right = None
+		self.parent = None
+
+
+
+BTroot = BinaryTree(1)
+BTrootl = BinaryTree(2)
+BTrootr = BinaryTree(3)
+BTrootll = BinaryTree(4)
+BTrootlr = BinaryTree(5)
+BTrootrl = BinaryTree(6)
+BTrootrr = BinaryTree(7)
+BTroot.left = BTrootl
+BTroot.right = BTrootr
+BTrootr.left = BTrootrl
+BTrootr.parent = BTroot
+BTrootl.parent = BTroot
+BTrootr.right = BTrootrr
+BTrootl.left = BTrootll
+BTrootl.right = BTrootlr
+BTrootrr.parent = BTrootr
+BTrootrl.parent = BTrootr
+BTrootlr.parent = BTrootl
+BTrootll.parent = BTrootl
+
+def lca(root, p, q):
+	q = [root]
+	level = 0
+	pLoc = (None, 0)
+	qLoc = (None, 0)
+	while q:
+		curSize = len(q)
+		for i in range(curSize):
+			curr = q.pop(0)
+			if curr == p:
+				pLoc = (curr, level)
+			elif curr == q:
+				qLoc = (curr, level)
+
+			if curr.left:
+				q.append(curr.left)
+			if curr.right:
+				q.append(curr.right)
+		level += 1
+
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