diff options
Diffstat (limited to 'scratch/deepmind')
| -rw-r--r-- | scratch/deepmind/part_two/balanced-binary-tree.py | 126 | ||||
| -rw-r--r-- | scratch/deepmind/part_two/todo.org | 4 |
2 files changed, 128 insertions, 2 deletions
diff --git a/scratch/deepmind/part_two/balanced-binary-tree.py b/scratch/deepmind/part_two/balanced-binary-tree.py new file mode 100644 index 000000000000..03de0350d898 --- /dev/null +++ b/scratch/deepmind/part_two/balanced-binary-tree.py @@ -0,0 +1,126 @@ +import unittest +from collections import deque + + +# is_balanced :: Node(a) -> Bool +def is_balanced(node): + q = deque() + q.append((0, node)) + mn, mx = None, None + + while q: + depth, node = q.popleft() + # Current node is a leaf node + if not node.left and not node.right: + mx = depth if mx is None else max(mx, depth) + mn = depth if mn is None else min(mn, depth) + if mx - mn > 1: + return False + if node.left: + q.append((depth + 1, node.left)) + if node.right: + q.append((depth + 1, node.right)) + + return mx - mn <= 1 + + +# Tests +class Test(unittest.TestCase): + class BinaryTreeNode(object): + def __init__(self, value): + self.value = value + self.left = None + self.right = None + + def insert_left(self, value): + self.left = Test.BinaryTreeNode(value) + return self.left + + def insert_right(self, value): + self.right = Test.BinaryTreeNode(value) + return self.right + + def test_full_tree(self): + tree = Test.BinaryTreeNode(5) + left = tree.insert_left(8) + right = tree.insert_right(6) + left.insert_left(1) + left.insert_right(2) + right.insert_left(3) + right.insert_right(4) + result = is_balanced(tree) + self.assertTrue(result) + + def test_both_leaves_at_the_same_depth(self): + tree = Test.BinaryTreeNode(3) + left = tree.insert_left(4) + right = tree.insert_right(2) + left.insert_left(1) + right.insert_right(9) + result = is_balanced(tree) + self.assertTrue(result) + + def test_leaf_heights_differ_by_one(self): + tree = Test.BinaryTreeNode(6) + left = tree.insert_left(1) + right = tree.insert_right(0) + right.insert_right(7) + result = is_balanced(tree) + self.assertTrue(result) + + def test_leaf_heights_differ_by_two(self): + tree = Test.BinaryTreeNode(6) + left = tree.insert_left(1) + right = tree.insert_right(0) + right_right = right.insert_right(7) + right_right.insert_right(8) + result = is_balanced(tree) + self.assertFalse(result) + + def test_three_leaves_total(self): + tree = Test.BinaryTreeNode(1) + left = tree.insert_left(5) + right = tree.insert_right(9) + right.insert_left(8) + right.insert_right(5) + result = is_balanced(tree) + self.assertTrue(result) + + def test_both_subtrees_superbalanced(self): + tree = Test.BinaryTreeNode(1) + left = tree.insert_left(5) + right = tree.insert_right(9) + right_left = right.insert_left(8) + right.insert_right(5) + right_left.insert_left(7) + result = is_balanced(tree) + self.assertFalse(result) + + def test_both_subtrees_superbalanced_two(self): + tree = Test.BinaryTreeNode(1) + left = tree.insert_left(2) + right = tree.insert_right(4) + left.insert_left(3) + left_right = left.insert_right(7) + left_right.insert_right(8) + right_right = right.insert_right(5) + right_right_right = right_right.insert_right(6) + right_right_right.insert_right(9) + result = is_balanced(tree) + self.assertFalse(result) + + def test_only_one_node(self): + tree = Test.BinaryTreeNode(1) + result = is_balanced(tree) + self.assertTrue(result) + + def test_linked_list_tree(self): + tree = Test.BinaryTreeNode(1) + right = tree.insert_right(2) + right_right = right.insert_right(3) + right_right.insert_right(4) + result = is_balanced(tree) + self.assertTrue(result) + + +unittest.main(verbosity=2) diff --git a/scratch/deepmind/part_two/todo.org b/scratch/deepmind/part_two/todo.org index 473973c415fc..3ddd9206ac9d 100644 --- a/scratch/deepmind/part_two/todo.org +++ b/scratch/deepmind/part_two/todo.org @@ -21,7 +21,7 @@ ** DONE Top Scores ** DONE Merging Meeting Times * Trees and graphs -** TODO Balanced Binary Tree +** DONE Balanced Binary Tree ** TODO Binary Search Tree Checker ** TODO 2nd Largest Item in a Binary Search Tree ** TODO Graph Coloring @@ -32,7 +32,7 @@ ** TODO Compute nth Fibonacci Number ** TODO Making Change ** TODO The Cake Thief -** TODO Balanced Binary Tree +** DONE Balanced Binary Tree ** TODO Binary Search Tree Checker ** TODO 2nd Largest Item in a Binary Search Tree * Queues and stacks |