diff --git a/arrays_strings/group_items/group_ordered_solution.ipynb b/arrays_strings/group_items/group_ordered_solution.ipynb
index b7d8b00..9441421 100644
--- a/arrays_strings/group_items/group_ordered_solution.ipynb
+++ b/arrays_strings/group_items/group_ordered_solution.ipynb
@@ -4,7 +4,7 @@
"cell_type": "markdown",
"metadata": {},
"source": [
- "This notebook was prepared by [Author](https://github.com/). Source and license info is on [GitHub](https://github.com/donnemartin/interactive-coding-challenges)."
+ "This notebook was prepared by [wdonahoe](https://github.com/wdonahoe). Source and license info is on [GitHub](https://github.com/donnemartin/interactive-coding-challenges)."
]
},
{
@@ -18,12 +18,14 @@
"cell_type": "markdown",
"metadata": {},
"source": [
- "## Problem: Implement foo(val), which returns val\n",
+ "## Problem: Implement a function that groups identical items based on their order in the list.\n",
"\n",
"* [Constraints](#Constraints)\n",
"* [Test Cases](#Test-Cases)\n",
- "* [Algorithm](#Algorithm)\n",
- "* [Code](#Code)\n",
+ "* [Algorithm: Modified Selection Sort](#Algorithm: Modified Selection Sort)\n",
+ "* [Code: Modified Selection Sort](#Code: Modified Selection Sort)\n",
+ "* [Algorithm: Ordered Dict](#Algorithm: Ordered Dict)\n",
+ "* [Code: Ordered Dict](#Code:-Ordered-Dict)\n",
"* [Unit Test](#Unit-Test)"
]
},
@@ -33,9 +35,8 @@
"source": [
"## Constraints\n",
"\n",
-
- "* Is it foo or bar?\n",
- " * foo"
+ "* Can we use extra data structures?\n",
+ " * Yes"
]
},
{
@@ -44,82 +45,118 @@
"source": [
"## Test Cases\n",
"\n",
- "* foo(val) -> val"
+ "* group_ordered([1,2,1,3,2]) -> [1,1,2,2,3]\n",
+ "* group_ordered(['a','b','a') -> ['a','a','b']\n",
+ "* group_ordered([1,1,2,3,4,5,2,1]-> [1,1,1,2,2,3,4,5]\n",
+ "* group_ordered([]) -> []\n",
+ "* group_ordered([1]) -> [1]\n",
+ "* group_ordered(None) -> None\n"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
- "## Algorithm\n",
+ "## Algorithm: Modified Selection Sort\n",
"\n",
- "Return the input, val\n",
+ "* Save the relative position of the first-occurence of each item in a list.\n",
+ "* Iterate through list of unique items.\n",
+ " * Keep an outer index; scan rest of list, swapping matching items with outer index and incrementing outer index each time. \n",
" \n",
"Complexity:\n",
- "* Time: O(1)\n",
- "* Space: O(1)"
+ "* Time: O(n^2)\n",
+ "* Space: O(n)"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
- "## Code"
+ "# Code: Modified Selection Sort"
]
},
{
"cell_type": "code",
- "execution_count": 1,
+ "execution_count": 5,
"metadata": {
"collapsed": false
},
"outputs": [],
"source": [
- "def foo(val):\n",
- " return val"
+ "def make_order_list(list_in):\n",
+ " order_list = []\n",
+ " for item in list_in:\n",
+ " if item not in order_list:\n",
+ " order_list.append(item)\n",
+ " return order_list\n",
+ "\n",
+ "\n",
+ "def group_ordered(list_in):\n",
+ " if list_in is None:\n",
+ " return None\n",
+ " order_list = make_order_list(list_in)\n",
+ " current = 0\n",
+ " for item in order_list:\n",
+ " search = current + 1\n",
+ " while True:\n",
+ " try:\n",
+ " if list_in[search] != item:\n",
+ " search += 1\n",
+ " else:\n",
+ " current += 1\n",
+ " list_in[current], list_in[search] = list_in[search], list_in[current]\n",
+ " search += 1\n",
+ " except IndexError:\n",
+ " break\n",
+ " return list_in"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
- "## Unit Test"
+ "## Algorithm: Ordered Dict.\n",
+ "\n",
+ "* Use an ordered dict to track insertion order of each key\n",
+ "* Flatten list of values.\n",
+ "\n",
+ "Complexity:\n",
+ "\n",
+ "* Time: O(n)\n",
+ "* Space: O(n)"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "metadata": {},
+ "source": [
+ "## Code: Ordered Dict"
]
},
{
"cell_type": "code",
- "execution_count": 2,
+ "execution_count": null,
"metadata": {
- "collapsed": false
+ "collapsed": true
},
- "outputs": [
- {
- "name": "stdout",
- "output_type": "stream",
- "text": [
- "Overwriting test_foo.py\n"
- ]
- }
- ],
+ "outputs": [],
"source": [
- "%%writefile test_foo.py\n",
- "from nose.tools import assert_equal\n",
+ "from collections import OrderedDict\n",
"\n",
+ "def group_ordered(list_in):\n",
+ " result = OrderedDict()\n",
+ " for value in list_in:\n",
+ " result.setdefault(value, []).append(value)\n",
+ " return [v for group in result.values() for v in group]"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "metadata": {},
+ "source": [
+ "## Unit Test\n",
"\n",
- "class TestFoo(object):\n",
- "\n",
- " def test_foo(self):\n",
- " assert_equal(foo(None), None)\n",
- " assert_equal(foo(0), 0)\n",
- " assert_equal(foo('bar'), 'bar')\n",
- " print('Success: test_foo')\n",
- "\n",
- "def main():\n",
- " test = TestFoo()\n",
- " test.test_foo()\n",
- "\n",
- "if __name__ == '__main__':\n",
- " main()"
+ "#### The following unit test is expected to fail until you solve the challenge."
]
},
{
@@ -133,16 +170,47 @@
"name": "stdout",
"output_type": "stream",
"text": [
- "Success: test_foo\n"
+ "Overwriting test_group_ordered.py\n"
]
}
],
"source": [
- "%run -i test_foo.py"
+ "%%writefile test_group_ordered.py\n",
+ "from nose.tools import assert_equal\n",
+ "\n",
+ "class TestGroupOrdered(object):\n",
+ "\n",
+ " def test_group_ordered(self):\n",
+ " assert_equal(group_ordered(None), None)\n",
+ " assert_equal(group_ordered([]), [])\n",
+ " assert_equal(group_ordered([1]), [1])\n",
+ " assert_equal(group_ordered([1,2,1,3,2]),[1,1,2,2,3])\n",
+ " assert_equal(group_ordered(['a','b','a']),['a','a','b'])\n",
+ " assert_equal(group_ordered([1,1,2,3,4,5,2,1]),[1,1,1,2,2,3,4,5])\n",
+ " assert_equal(group_ordered([1,2,3,4,3,4]),[1,2,3,3,4,4])\n",
+ "\n",
+ "def main():\n",
+ " test = TestGroupOrdered()\n",
+ " test.test_group_ordered()\n",
+ "\n",
+ "if __name__ == '__main__':\n",
+ " main()\n"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": 4,
+ "metadata": {
+ "collapsed": false
+ },
+ "outputs": [],
+ "source": [
+ "%run -i test_group_ordered.py"
]
}
],
"metadata": {
+ "celltoolbar": "Edit Metadata",
"kernelspec": {
"display_name": "Python 2",
"language": "python",
@@ -158,7 +226,7 @@
"name": "python",
"nbconvert_exporter": "python",
"pygments_lexer": "ipython2",
- "version": "2.7.10"
+ "version": "2.7.6"
}
},
"nbformat": 4,