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Reworked notebook: Added more detail to constraints and test cases. Reworked code and unit test.

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Donne Martin 2015-06-26 05:07:44 -04:00
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128
linked-lists/partition.ipynb
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@ -13,21 +13,28 @@
"source": [
"## Problem: Partition a linked list around a value x, such that all nodes less than x come before all nodes greater than or equal to x.\n",
"\n",
"* [Clarifying Questions](#Clarifying-Questions)\n",
"* [Constraints and Assumptions](#Constraints-and-Assumptions)\n",
"* [Test Cases](#Test-Cases)\n",
"* [Algorithm](#Algorithm)\n",
"* [Code](#Code)"
"* [Code](#Code)\n",
"* [Unit Test](#Unit-Test)"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Clarifying Questions\n",
"## Constraints and Assumptions\n",
"\n",
"*Problem statements are often intentionally ambiguous. Identifying constraints and stating assumptions can help to ensure you code the intended solution.*\n",
"\n",
"* Can we create additional data structures?\n",
" * Yes\n",
"* Do you expect the function to return a new list?\n",
" * Yes\n",
"* Can we assume the input x is valid?\n",
" * Yes\n",
"* Can we assume we already have a linked list class that can be used for this problem?\n",
" * Yes"
]
},
@ -41,7 +48,6 @@
"* One element list\n",
"* Left linked list is empty\n",
"* Right linked list is empty\n",
"* X invalid\n",
"* General case\n",
" * Partition = 10\n",
" * Input: 4, 3, 7, 8, 10, 1, 10, 12\n",
@ -54,7 +60,6 @@
"source": [
"## Algorithm\n",
"\n",
"* Test error cases\n",
"* Create left and right linked lists\n",
"* For each element in the list\n",
" * If elem < x, append to the left list\n",
@ -75,7 +80,7 @@
},
{
"cell_type": "code",
"execution_count": null,
"execution_count": 1,
"metadata": {
"collapsed": true
},
@ -86,9 +91,9 @@
},
{
"cell_type": "code",
"execution_count": null,
"execution_count": 2,
"metadata": {
"collapsed": true
"collapsed": false
},
"outputs": [],
"source": [
@ -96,11 +101,11 @@
" def partition(self, data):\n",
" if self.head is None:\n",
" return\n",
" if type(data) != int:\n",
" raise ValueError('Invalid int argument: data')\n",
" left = MyLinkedList(None)\n",
" right = MyLinkedList(None)\n",
" curr = self.head\n",
" \n",
" # Build the left and right lists\n",
" while curr is not None:\n",
" if curr.data < data:\n",
" left.append(curr.data)\n",
@ -111,52 +116,87 @@
" if curr_left is None:\n",
" return right\n",
" else:\n",
" # Merge the two lists\n",
" while curr_left.next is not None:\n",
" curr_left = curr_left.next\n",
" curr_left.next = right.head\n",
" return left"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Unit Test"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"*It is important to identify and run through general and edge cases from the [Test Cases](#Test-Cases) section by hand. You generally will not be asked to write a unit test like what is shown below.*"
]
},
{
"cell_type": "code",
"execution_count": null,
"execution_count": 3,
"metadata": {
"collapsed": false
},
"outputs": [],
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"Test: Empty list\n",
"Test: One element list, left list empty\n",
"Test: Right list is empty\n",
"Test: General case\n",
"Success: test_partition\n"
]
}
],
"source": [
"print('Empty list')\n",
"linked_list = MyLinkedList(None)\n",
"linked_list.partition(10)\n",
"linked_list.print_list()\n",
"print('X invalid')\n",
"head = Node(12)\n",
"linked_list = MyLinkedList(head)\n",
"try:\n",
" linked_list.partition('a')\n",
"except ValueError as err:\n",
" print(err)\n",
"linked_list.print_list()\n",
"print('One element list')\n",
"print('Left linked list is empty')\n",
"linked_list.partition(1)\n",
"linked_list.print_list()\n",
"print('Right linked list is empty')\n",
"linked_list.partition(20)\n",
"linked_list.print_list()\n",
"print('General case')\n",
"# Partition = 10\n",
"# Input 4, 3, 7, 8, 10, 1, 10, 12\n",
"# Output 4, 3, 7, 8, 1, 10, 10, 12\n",
"linked_list.insert_to_front(10)\n",
"linked_list.insert_to_front(1)\n",
"linked_list.insert_to_front(10)\n",
"linked_list.insert_to_front(8)\n",
"linked_list.insert_to_front(7)\n",
"linked_list.insert_to_front(3)\n",
"linked_list.insert_to_front(4)\n",
"partitioned_list = linked_list.partition(10)\n",
"partitioned_list.print_list()"
"from nose.tools import assert_equal\n",
"\n",
"class Test(object):\n",
" def test_partition(self):\n",
" print('Test: Empty list')\n",
" linked_list = MyLinkedList(None)\n",
" linked_list.partition(10)\n",
" assert_equal(linked_list.get_all_data(), [])\n",
"\n",
" print('Test: One element list, left list empty')\n",
" linked_list = MyLinkedList(Node(5))\n",
" linked_list.partition(0)\n",
" assert_equal(linked_list.get_all_data(), [5])\n",
"\n",
" print('Test: Right list is empty')\n",
" linked_list = MyLinkedList(Node(5))\n",
" linked_list.partition(10)\n",
" assert_equal(linked_list.get_all_data(), [5])\n",
"\n",
" print('Test: General case')\n",
" # Partition = 10\n",
" # Input: 4, 3, 7, 8, 10, 1, 10, 12\n",
" # Output: 4, 3, 7, 8, 1, 10, 10, 12\n",
" linked_list = MyLinkedList(Node(12))\n",
" linked_list.insert_to_front(10)\n",
" linked_list.insert_to_front(1)\n",
" linked_list.insert_to_front(10)\n",
" linked_list.insert_to_front(8)\n",
" linked_list.insert_to_front(7)\n",
" linked_list.insert_to_front(3)\n",
" linked_list.insert_to_front(4)\n",
" partitioned_list = linked_list.partition(10)\n",
" assert_equal(partitioned_list.get_all_data(), \n",
" [4, 3, 7, 8, 1, 10, 10, 12])\n",
" \n",
" print('Success: test_partition')\n",
"\n",
"if __name__ == '__main__':\n",
" test = Test()\n",
" test.test_partition()"
]
}
],