diff --git a/graphs_trees/check_balance/check_balance_challenge.ipynb b/graphs_trees/check_balance/check_balance_challenge.ipynb index e0d9756..e29d7f4 100644 --- a/graphs_trees/check_balance/check_balance_challenge.ipynb +++ b/graphs_trees/check_balance/check_balance_challenge.ipynb @@ -92,9 +92,11 @@ }, "outputs": [], "source": [ - "def check_balance(root):\n", - " # TODO: Implement me\n", - " pass" + "class BstBalance(Bst):\n", + "\n", + " def check_balance(self):\n", + " # TODO: Implement me\n", + " pass" ] }, { @@ -128,33 +130,34 @@ "\n", " @raises(Exception)\n", " def test_check_balance_empty(self):\n", - " check_balance(None)\n", + " bst = BstBalance(None)\n", + " bst.check_balance()\n", "\n", " def test_check_balance(self):\n", - " node = Node(5)\n", - " assert_equal(check_balance(node), True)\n", + " bst = BstBalance(Node(5))\n", + " assert_equal(bst.check_balance(), True)\n", "\n", - " insert(node, 3)\n", - " insert(node, 8)\n", - " insert(node, 1)\n", - " insert(node, 4)\n", - " assert_equal(check_balance(node), True)\n", + " bst.insert(3)\n", + " bst.insert(8)\n", + " bst.insert(1)\n", + " bst.insert(4)\n", + " assert_equal(bst.check_balance(), True)\n", "\n", - " node = Node(5)\n", - " insert(node, 3)\n", - " insert(node, 8)\n", - " insert(node, 9)\n", - " insert(node, 10)\n", - " assert_equal(check_balance(node), False)\n", + " bst = BstBalance(Node(5))\n", + " bst.insert(3)\n", + " bst.insert(8)\n", + " bst.insert(9)\n", + " bst.insert(10)\n", + " assert_equal(bst.check_balance(), 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", + " bst = BstBalance(Node(3))\n", + " bst.insert(2)\n", + " bst.insert(1)\n", + " bst.insert(5)\n", + " bst.insert(4)\n", + " bst.insert(6)\n", + " bst.insert(7)\n", + " assert_equal(bst.check_balance(), True)\n", "\n", " print('Success: test_check_balance')\n", "\n", diff --git a/graphs_trees/check_balance/check_balance_solution.ipynb b/graphs_trees/check_balance/check_balance_solution.ipynb index d60dc53..ed83414 100644 --- a/graphs_trees/check_balance/check_balance_solution.ipynb +++ b/graphs_trees/check_balance/check_balance_solution.ipynb @@ -66,11 +66,10 @@ "However, we could check whether the tree is balanced while also checking for the heights.\n", "\n", "* Base case: If the root is None, return 0\n", - "* Recursively check whether the left sub tree is balanced, and get its maximum and minimum height\n", - "* Recursively Check whether the right sub tree is balanced, and get its maximum and minimum height\n", - "* Calculate the maximum height and minimum height of the current tree\n", - "* If both sub-trees are balanced, and the maximum and minimum height of the current tree doesn't differ by more than 1, then the current tree is balanced. Otherwise, it is not\n", - "* Return whether the current tree is balanced, and the maximum height and minimum height of the current tree\n", + "* Recursively check whether the left sub tree is balanced, and get its height left_height\n", + "* Recursively check whether the right sub tree is balanced, and get its height right_height\n", + "* Compare left_height and right_height\n", + "* Return 1 + max(left_height, right_height)\n", " \n", "Complexity:\n", "* Time: O(n)\n", @@ -99,26 +98,31 @@ "cell_type": "code", "execution_count": 2, "metadata": { - "collapsed": false + "collapsed": true }, "outputs": [], "source": [ - "def _check_balance(root):\n", - " if root is None:\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 = 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", + "class BstBalance(Bst):\n", "\n", + " def _check_height(self, node):\n", + " if node is None:\n", + " return 0\n", + " left_height = self._check_height(node.left)\n", + " if left_height == -1:\n", + " return -1\n", + " right_height = self._check_height(node.right)\n", + " if right_height == -1:\n", + " return -1\n", + " diff = abs(left_height-right_height)\n", + " if diff > 1:\n", + " return -1\n", + " return 1 + max(left_height, right_height)\n", "\n", - "def check_balance(root):\n", - " if root is None:\n", - " raise Exception('No root node')\n", - " balanced, _, _ = _check_balance(root)\n", - " return balanced" + " def check_balance(self):\n", + " if self.root is None:\n", + " raise Exception('No root node')\n", + " height = self._check_height(self.root)\n", + " return height != -1" ] }, { @@ -153,33 +157,34 @@ "\n", " @raises(Exception)\n", " def test_check_balance_empty(self):\n", - " check_balance(None)\n", + " bst = BstBalance(None)\n", + " bst.check_balance()\n", "\n", " def test_check_balance(self):\n", - " node = Node(5)\n", - " assert_equal(check_balance(node), True)\n", + " bst = BstBalance(Node(5))\n", + " assert_equal(bst.check_balance(), True)\n", "\n", - " insert(node, 3)\n", - " insert(node, 8)\n", - " insert(node, 1)\n", - " insert(node, 4)\n", - " assert_equal(check_balance(node), True)\n", + " bst.insert(3)\n", + " bst.insert(8)\n", + " bst.insert(1)\n", + " bst.insert(4)\n", + " assert_equal(bst.check_balance(), True)\n", "\n", - " node = Node(5)\n", - " insert(node, 3)\n", - " insert(node, 8)\n", - " insert(node, 9)\n", - " insert(node, 10)\n", - " assert_equal(check_balance(node), False)\n", + " bst = BstBalance(Node(5))\n", + " bst.insert(3)\n", + " bst.insert(8)\n", + " bst.insert(9)\n", + " bst.insert(10)\n", + " assert_equal(bst.check_balance(), 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", + " bst = BstBalance(Node(3))\n", + " bst.insert(2)\n", + " bst.insert(1)\n", + " bst.insert(5)\n", + " bst.insert(4)\n", + " bst.insert(6)\n", + " bst.insert(7)\n", + " assert_equal(bst.check_balance(), True)\n", "\n", " print('Success: test_check_balance')\n", "\n", diff --git a/graphs_trees/check_balance/test_check_balance.py b/graphs_trees/check_balance/test_check_balance.py index 13dafd4..831f96c 100644 --- a/graphs_trees/check_balance/test_check_balance.py +++ b/graphs_trees/check_balance/test_check_balance.py @@ -6,33 +6,34 @@ class TestCheckBalance(object): @raises(Exception) def test_check_balance_empty(self): - check_balance(None) + bst = BstBalance(None) + bst.check_balance() def test_check_balance(self): - node = Node(5) - assert_equal(check_balance(node), True) + bst = BstBalance(Node(5)) + assert_equal(bst.check_balance(), True) - insert(node, 3) - insert(node, 8) - insert(node, 1) - insert(node, 4) - assert_equal(check_balance(node), True) + bst.insert(3) + bst.insert(8) + bst.insert(1) + bst.insert(4) + assert_equal(bst.check_balance(), True) - node = Node(5) - insert(node, 3) - insert(node, 8) - insert(node, 9) - insert(node, 10) - assert_equal(check_balance(node), False) + bst = BstBalance(Node(5)) + bst.insert(3) + bst.insert(8) + bst.insert(9) + bst.insert(10) + assert_equal(bst.check_balance(), False) - node = Node(3) - insert(node, 2) - insert(node, 1) - insert(node, 5) - insert(node, 4) - insert(node, 6) - insert(node, 7) - assert_equal(check_balance(node), False) + bst = BstBalance(Node(3)) + bst.insert(2) + bst.insert(1) + bst.insert(5) + bst.insert(4) + bst.insert(6) + bst.insert(7) + assert_equal(bst.check_balance(), True) print('Success: test_check_balance')