From 7882ed9ae7ae2f8e0e500fe2374a8d48dbcc244d Mon Sep 17 00:00:00 2001 From: Donne Martin Date: Sat, 25 Jun 2016 08:42:16 -0400 Subject: [PATCH] Polish check tree balance challenge and solution (#80) Update constraints, test cases, tests, and code. --- .../check_balance_challenge.ipynb | 29 ++++++++++++--- .../check_balance_solution.ipynb | 36 ++++++++++++------- .../check_balance/test_check_balance.py | 4 +++ 3 files changed, 52 insertions(+), 17 deletions(-) diff --git a/graphs_trees/check_balance/check_balance_challenge.ipynb b/graphs_trees/check_balance/check_balance_challenge.ipynb index 3f13284..bcd1fb4 100644 --- a/graphs_trees/check_balance/check_balance_challenge.ipynb +++ b/graphs_trees/check_balance/check_balance_challenge.ipynb @@ -36,7 +36,11 @@ "\n", "* Is a balanced tree one where the heights of two sub trees of any node doesn't differ by more than 1?\n", " * Yes\n", + "* If this is called on a None input, should we return False?\n", + " * Yes\n", "* Can we assume we already have a Node class with an insert method?\n", + " * Yes\n", + "* Can we assume this fits memory?\n", " * Yes" ] }, @@ -46,6 +50,8 @@ "source": [ "## Test Cases\n", "\n", + "* None -> No\n", + "* 1 -> Yes\n", "* 5, 3, 8, 1, 4 -> Yes\n", "* 5, 3, 8, 9, 10 -> No" ] @@ -120,7 +126,11 @@ "class TestCheckBalance(object):\n", "\n", " def test_check_balance(self):\n", + " assert_equal(check_balance(None), False)\n", + "\n", " node = Node(5)\n", + " assert_equal(check_balance(node), True)\n", + "\n", " insert(node, 3)\n", " insert(node, 8)\n", " insert(node, 1)\n", @@ -134,6 +144,15 @@ " insert(node, 10)\n", " assert_equal(check_balance(node), False)\n", "\n", + " node = Node(3)\n", + " insert(node, 2)\n", + " insert(node, 1)\n", + " insert(node, 5)\n", + " insert(node, 4)\n", + " insert(node, 6)\n", + " insert(node, 7)\n", + " assert_equal(check_balance(node), False)\n", + "\n", " print('Success: test_check_balance')\n", "\n", "\n", @@ -158,21 +177,21 @@ ], "metadata": { "kernelspec": { - "display_name": "Python 2", + "display_name": "Python 3", "language": "python", - "name": "python2" + "name": "python3" }, "language_info": { "codemirror_mode": { "name": "ipython", - "version": 2 + "version": 3 }, "file_extension": ".py", "mimetype": "text/x-python", "name": "python", "nbconvert_exporter": "python", - "pygments_lexer": "ipython2", - "version": "2.7.10" + "pygments_lexer": "ipython3", + "version": "3.5.0" } }, "nbformat": 4, diff --git a/graphs_trees/check_balance/check_balance_solution.ipynb b/graphs_trees/check_balance/check_balance_solution.ipynb index d7505f9..775b786 100644 --- a/graphs_trees/check_balance/check_balance_solution.ipynb +++ b/graphs_trees/check_balance/check_balance_solution.ipynb @@ -35,7 +35,11 @@ "\n", "* Is a balanced tree one where the heights of two sub trees of any node doesn't differ by more than 1?\n", " * Yes\n", + "* If this is called on a None input, should we return False?\n", + " * Yes\n", "* Can we assume we already have a Node class with an insert method?\n", + " * Yes\n", + "* Can we assume this fits memory?\n", " * Yes" ] }, @@ -45,6 +49,8 @@ "source": [ "## Test Cases\n", "\n", + "* None -> No\n", + "* 1 -> Yes\n", "* 5, 3, 8, 1, 4 -> Yes\n", "* 5, 3, 8, 9, 10 -> No" ] @@ -97,18 +103,20 @@ }, "outputs": [], "source": [ - "def __check_balance__(root):\n", + "def _check_balance(root):\n", " if not root:\n", " return (True, 0, 0)\n", - " left_balanced, left_min_h, left_max_h = __check_balance__(root.left)\n", - " right_balanced, right_min_h, right_max_h = __check_balance__(root.right)\n", - " min_h = min(left_min_h, right_min_h) + 1\n", - " max_h = max(left_max_h, right_max_h) + 1\n", - " balanced = left_balanced and right_balanced and abs(max_h - min_h) <= 1\n", + " left_balanced, left_min_h, left_max_h = _check_balance(root.left)\n", + " right_balanced, right_min_h, right_max_h = _check_balance(root.right)\n", + " min_h = 1 + min(left_min_h, right_min_h)\n", + " max_h = 1 + max(left_max_h, right_max_h)\n", + " balanced = left_balanced and right_balanced and abs(max_h-min_h) <= 1\n", " return (balanced, min_h, max_h)\n", "\n", "def check_balance(root):\n", - " balanced, _, _ = __check_balance__(root)\n", + " if root is None:\n", + " return False\n", + " balanced, _, _ = _check_balance(root)\n", " return balanced" ] }, @@ -142,7 +150,11 @@ "class TestCheckBalance(object):\n", "\n", " def test_check_balance(self):\n", + " assert_equal(check_balance(None), False)\n", + "\n", " node = Node(5)\n", + " assert_equal(check_balance(node), True)\n", + "\n", " insert(node, 3)\n", " insert(node, 8)\n", " insert(node, 1)\n", @@ -199,21 +211,21 @@ ], "metadata": { "kernelspec": { - "display_name": "Python 2", + "display_name": "Python 3", "language": "python", - "name": "python2" + "name": "python3" }, "language_info": { "codemirror_mode": { "name": "ipython", - "version": 2 + "version": 3 }, "file_extension": ".py", "mimetype": "text/x-python", "name": "python", "nbconvert_exporter": "python", - "pygments_lexer": "ipython2", - "version": "2.7.10" + "pygments_lexer": "ipython3", + "version": "3.5.0" } }, "nbformat": 4, diff --git a/graphs_trees/check_balance/test_check_balance.py b/graphs_trees/check_balance/test_check_balance.py index c53bcf3..843ba6c 100644 --- a/graphs_trees/check_balance/test_check_balance.py +++ b/graphs_trees/check_balance/test_check_balance.py @@ -4,7 +4,11 @@ from nose.tools import assert_equal class TestCheckBalance(object): def test_check_balance(self): + assert_equal(check_balance(None), False) + node = Node(5) + assert_equal(check_balance(node), True) + insert(node, 3) insert(node, 8) insert(node, 1)