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Polish bst validate challenge and solution (#83)

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Update constraints, test cases, tests, algorithm discussion, and code.
This commit is contained in:
Donne Martin
2016-06-25 22:08:54 -04:00
committed by GitHub
parent 7b573ceaa3
commit 589ff06b15
3 changed files with 46 additions and 15 deletions
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34
graphs_trees/bst_validate/bst_validate_solution.ipynb
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@@ -35,7 +35,11 @@
"\n",
"* Can the tree have duplicates?\n",
" * Yes\n",
"* If this is called on a None input, should we raise an exception?\n",
" * Yes\n",
"* Can we assume we already have a Node class?\n",
" * Yes\n",
"* Can we assume this fits in memory?\n",
" * Yes"
]
},
@@ -45,6 +49,8 @@
"source": [
"## Test Cases\n",
"\n",
"None -> exception\n",
"\n",
"<pre>\n",
"Valid:\n",
" 5\n",
@@ -70,7 +76,7 @@
"\n",
"We'll use a recursive solution that valides left <= current < right, passing down the min and max values as we do a depth-first traversal.\n",
"\n",
"* If the node is None, return False\n",
"* If the node is None, return True\n",
"* If min is set and the node's value <= min, return False\n",
"* if max is set and the node's value > max, return False\n",
"* Recursively call the validate function on node.left, updating max\n",
@@ -108,19 +114,21 @@
"outputs": [],
"source": [
"def validate_bst(node):\n",
" return __validate_bst__(node, None, None)\n",
" if node is None:\n",
" raise Exception('No root node')\n",
" return _validate_bst(node, None, None)\n",
"\n",
"\n",
"def __validate_bst__(node, mininum, maximum):\n",
"def _validate_bst(node, mininum, maximum):\n",
" if node is None:\n",
" return True\n",
" if mininum is not None and node.data <= mininum:\n",
" return False\n",
" if maximum is not None and node.data > maximum:\n",
" return False\n",
" if not __validate_bst__(node.left, mininum, node.data):\n",
" if not _validate_bst(node.left, mininum, node.data):\n",
" return False\n",
" if not __validate_bst__(node.right, node.data, maximum):\n",
" if not _validate_bst(node.right, node.data, maximum):\n",
" return False\n",
" return True"
]
@@ -150,10 +158,15 @@
"source": [
"%%writefile test_bst_validate.py\n",
"from nose.tools import assert_equal\n",
"from nose.tools import raises\n",
"\n",
"\n",
"class TestBstValidate(object):\n",
"\n",
" @raises(Exception)\n",
" def test_bst_validate_empty(self):\n",
" validate_bst(None)\n",
"\n",
" def test_bst_validate(self):\n",
" node = Node(5)\n",
" insert(node, 8)\n",
@@ -177,6 +190,7 @@
"\n",
"def main():\n",
" test = TestBstValidate()\n",
" test.test_bst_validate_empty()\n",
" test.test_bst_validate()\n",
"\n",
"\n",
@@ -206,21 +220,21 @@
],
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"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",
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}
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"nbformat": 4,