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

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Donne Martin 2015-06-26 05:07:19 -04:00
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125
linked-lists/palindrome.ipynb
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@ -13,21 +13,25 @@
"source": [
"## Problem: Determine if a linked list is a palindrome.\n",
"\n",
"* [Clarifying Questions](#Clarifying-Questions)\n",
"* [Constraints and Assumptions](#Constraints-and-Assumptions)\n",
"* [Test Cases](#Test-Cases)\n",
"* [Algorithm](#Algorithm)\n",
"* [Code](#Code)\n",
"* [Pythonic-Code](#Pythonic-Code)"
"* [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",
"* Is a single character or number a palindrome?\n",
" * No"
" * No\n",
"* Can we assume we already have a linked list class that can be used for this problem?\n",
" * Yes"
]
},
{
@ -36,6 +40,7 @@
"source": [
"## Test Cases\n",
"\n",
"\n",
"* Empty list\n",
"* Single element list\n",
"* Two element list, not a palindrome\n",
@ -71,7 +76,7 @@
},
{
"cell_type": "code",
"execution_count": null,
"execution_count": 1,
"metadata": {
"collapsed": true
},
@ -82,7 +87,7 @@
},
{
"cell_type": "code",
"execution_count": null,
"execution_count": 2,
"metadata": {
"collapsed": false
},
@ -95,10 +100,15 @@
" curr = self.head\n",
" reversed_list = MyLinkedList()\n",
" length = 0\n",
" \n",
" # Reverse the linked list\n",
" while curr is not None:\n",
" reversed_list.insert_to_front(curr.data)\n",
" length += 1\n",
" curr = curr.next\n",
" \n",
" # Compare the reversed list with the original list\n",
" # Only need to compare the first half \n",
" iterations_to_compare_half = length / 2\n",
" curr = self.head\n",
" curr_reversed = reversed_list.head\n",
@ -110,42 +120,85 @@
" return True"
]
},
{
"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: Single element list\n",
"Test: Two element list, not a palindrome\n",
"Test: Three element list, not a palindrome\n",
"Test: General case: Palindrome with even length\n",
"Test: General case: Palindrome with odd length\n",
"Success: test_is_palindrome\n"
]
}
],
"source": [
"print('Empty list')\n",
"linked_list = MyLinkedList()\n",
"print(linked_list.is_palindrome())\n",
"print('Single element list')\n",
"head = Node(1)\n",
"linked_list = MyLinkedList(head)\n",
"print(linked_list.is_palindrome())\n",
"print('Two element list, not a palindrome')\n",
"linked_list.append(2)\n",
"print(linked_list.is_palindrome())\n",
"print('Three element list, not a palindrome')\n",
"linked_list.append(3)\n",
"print(linked_list.is_palindrome())\n",
"print('General case: Palindrome with even length')\n",
"head = Node('a')\n",
"linked_list = MyLinkedList(head)\n",
"linked_list.append('b')\n",
"linked_list.append('b')\n",
"linked_list.append('a')\n",
"print(linked_list.is_palindrome())\n",
"print('General case: Palindrome with odd length')\n",
"head = Node(1)\n",
"linked_list = MyLinkedList(head)\n",
"linked_list.append(2)\n",
"linked_list.append(3)\n",
"linked_list.append(2)\n",
"linked_list.append(1)\n",
"print(linked_list.is_palindrome())"
"from nose.tools import assert_equal\n",
"\n",
"class Test(object):\n",
" def test_is_palindrome(self):\n",
" print('Test: Empty list')\n",
" linked_list = MyLinkedList()\n",
" assert_equal(linked_list.is_palindrome(), False)\n",
"\n",
" print('Test: Single element list')\n",
" head = Node(1)\n",
" linked_list = MyLinkedList(head)\n",
" assert_equal(linked_list.is_palindrome(), False)\n",
"\n",
" print('Test: Two element list, not a palindrome')\n",
" linked_list.append(2)\n",
" assert_equal(linked_list.is_palindrome(), False)\n",
"\n",
" print('Test: Three element list, not a palindrome')\n",
" linked_list.append(3)\n",
" assert_equal(linked_list.is_palindrome(), False)\n",
"\n",
" print('Test: General case: Palindrome with even length')\n",
" head = Node('a')\n",
" linked_list = MyLinkedList(head)\n",
" linked_list.append('b')\n",
" linked_list.append('b')\n",
" linked_list.append('a')\n",
" assert_equal(linked_list.is_palindrome(), True)\n",
"\n",
" print('Test: General case: Palindrome with odd length')\n",
" head = Node(1)\n",
" linked_list = MyLinkedList(head)\n",
" linked_list.append(2)\n",
" linked_list.append(3)\n",
" linked_list.append(2)\n",
" linked_list.append(1)\n",
" assert_equal(linked_list.is_palindrome(), True)\n",
" \n",
" print('Success: test_is_palindrome')\n",
"\n",
"if __name__ == '__main__':\n",
" test = Test()\n",
" test.test_is_palindrome()"
]
}
],