mirror of
https://github.com/donnemartin/interactive-coding-challenges
synced 2026-01-08 18:38:03 +00:00
Restructured packages.
This commit is contained in:
Donne Martin
297
stacks_queues/stack/stack.ipynb
Normal file
297
stacks_queues/stack/stack.ipynb
Normal file
@@ -0,0 +1,297 @@
|
||||
{
|
||||
"cells": [
|
||||
{
|
||||
"cell_type": "markdown",
|
||||
"metadata": {},
|
||||
"source": [
|
||||
"<small><i>This notebook was prepared by [Donne Martin](http://donnemartin.com). Source and license info is on [GitHub](https://bit.ly/code-notes).</i></small>"
|
||||
]
|
||||
},
|
||||
{
|
||||
"cell_type": "markdown",
|
||||
"metadata": {},
|
||||
"source": [
|
||||
"## Problem: Implement a stack with push, pop, peek, and is_empty methods using a linked list.\n",
|
||||
"\n",
|
||||
"* [Constraints and Assumptions](#Constraints-and-Assumptions)\n",
|
||||
"* [Test Cases](#Test-Cases)\n",
|
||||
"* [Algorithm](#Algorithm)\n",
|
||||
"* [Code](#Code)\n",
|
||||
"* [Unit Test](#Unit-Test)\n",
|
||||
"* [Pythonic-Code](#Pythonic-Code)"
|
||||
]
|
||||
},
|
||||
{
|
||||
"cell_type": "markdown",
|
||||
"metadata": {},
|
||||
"source": [
|
||||
"## 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",
|
||||
"* None"
|
||||
]
|
||||
},
|
||||
{
|
||||
"cell_type": "markdown",
|
||||
"metadata": {},
|
||||
"source": [
|
||||
"## Test Cases\n",
|
||||
"\n",
|
||||
"### Push\n",
|
||||
"\n",
|
||||
"* Push to empty stack\n",
|
||||
"* Push to non-empty stack\n",
|
||||
"\n",
|
||||
"### Pop\n",
|
||||
"\n",
|
||||
"* Pop on empty stack\n",
|
||||
"* Pop on single element stack\n",
|
||||
"* Pop on multiple element stack\n",
|
||||
"\n",
|
||||
"### Peek\n",
|
||||
"\n",
|
||||
"* Peek on empty stack\n",
|
||||
"* Peek on one or more element stack\n",
|
||||
"\n",
|
||||
"### Is Empty\n",
|
||||
"\n",
|
||||
"* Is empty on empty stack\n",
|
||||
"* Is empty on one or more element stack"
|
||||
]
|
||||
},
|
||||
{
|
||||
"cell_type": "markdown",
|
||||
"metadata": {},
|
||||
"source": [
|
||||
"## Algorithm\n",
|
||||
"\n",
|
||||
"### Push\n",
|
||||
"\n",
|
||||
"* Create new node with value\n",
|
||||
"* Set node's next to top\n",
|
||||
"* Set top to node\n",
|
||||
"\n",
|
||||
"Complexity:\n",
|
||||
"* Time: O(1)\n",
|
||||
"* Space: O(1)\n",
|
||||
"\n",
|
||||
"### Pop\n",
|
||||
"\n",
|
||||
"* If stack is empty, return NULL\n",
|
||||
"* Else \n",
|
||||
" * Save top's value\n",
|
||||
" * Set top to top.next\n",
|
||||
" * Return saved value\n",
|
||||
"\n",
|
||||
"Complexity:\n",
|
||||
"* Time: O(1)\n",
|
||||
"* Space: O(1)\n",
|
||||
"\n",
|
||||
"### Peek\n",
|
||||
"\n",
|
||||
"* If stack is empty, return NULL\n",
|
||||
"* Else return top's value\n",
|
||||
"\n",
|
||||
"Complexity:\n",
|
||||
"* Time: O(1)\n",
|
||||
"* Space: O(1)\n",
|
||||
"\n",
|
||||
"### Is Empty\n",
|
||||
"* If peek has a value, return False\n",
|
||||
"* Else return True\n",
|
||||
"\n",
|
||||
"Complexity:\n",
|
||||
"* Time: O(1)\n",
|
||||
"* Space: O(1)"
|
||||
]
|
||||
},
|
||||
{
|
||||
"cell_type": "markdown",
|
||||
"metadata": {},
|
||||
"source": [
|
||||
"## Code"
|
||||
]
|
||||
},
|
||||
{
|
||||
"cell_type": "code",
|
||||
"execution_count": 1,
|
||||
"metadata": {
|
||||
"collapsed": false
|
||||
},
|
||||
"outputs": [
|
||||
{
|
||||
"name": "stdout",
|
||||
"output_type": "stream",
|
||||
"text": [
|
||||
"Overwriting stack.py\n"
|
||||
]
|
||||
}
|
||||
],
|
||||
"source": [
|
||||
"%%writefile stack.py\n",
|
||||
"\n",
|
||||
"class Node(object):\n",
|
||||
" def __init__(self, data):\n",
|
||||
" self.data = data\n",
|
||||
" self.next = None\n",
|
||||
"\n",
|
||||
"class Stack(object):\n",
|
||||
" def __init__(self, top=None):\n",
|
||||
" self.top = top\n",
|
||||
"\n",
|
||||
" def push(self, data):\n",
|
||||
" node = Node(data)\n",
|
||||
" node.next = self.top\n",
|
||||
" self.top = node\n",
|
||||
"\n",
|
||||
" def pop(self):\n",
|
||||
" if self.top is not None:\n",
|
||||
" data = self.top.data\n",
|
||||
" self.top = self.top.next\n",
|
||||
" return data\n",
|
||||
" return None\n",
|
||||
"\n",
|
||||
" def peek(self):\n",
|
||||
" if self.top is not None:\n",
|
||||
" return self.top.data\n",
|
||||
" return None\n",
|
||||
"\n",
|
||||
" def is_empty(self):\n",
|
||||
" return self.peek() is None"
|
||||
]
|
||||
},
|
||||
{
|
||||
"cell_type": "code",
|
||||
"execution_count": 2,
|
||||
"metadata": {
|
||||
"collapsed": false
|
||||
},
|
||||
"outputs": [],
|
||||
"source": [
|
||||
"%run stack.py"
|
||||
]
|
||||
},
|
||||
{
|
||||
"cell_type": "markdown",
|
||||
"metadata": {},
|
||||
"source": [
|
||||
"## Unit Test\n",
|
||||
"\n",
|
||||
"*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": 3,
|
||||
"metadata": {
|
||||
"collapsed": false
|
||||
},
|
||||
"outputs": [
|
||||
{
|
||||
"name": "stdout",
|
||||
"output_type": "stream",
|
||||
"text": [
|
||||
"Test: Empty stack\n",
|
||||
"Test: One element\n",
|
||||
"Test: More than one element\n",
|
||||
"Success: test_end_to_end\n"
|
||||
]
|
||||
}
|
||||
],
|
||||
"source": [
|
||||
"from nose.tools import assert_equal\n",
|
||||
"\n",
|
||||
"class Test(object):\n",
|
||||
" # TODO: It would be better if we had unit tests for each\n",
|
||||
" # method in addition to the following end-to-end test\n",
|
||||
" def test_end_to_end(self):\n",
|
||||
" print('Test: Empty stack')\n",
|
||||
" stack = Stack()\n",
|
||||
" assert_equal(stack.peek(), None)\n",
|
||||
" assert_equal(stack.pop(), None)\n",
|
||||
"\n",
|
||||
" print('Test: One element')\n",
|
||||
" top = Node(5)\n",
|
||||
" stack = Stack(top)\n",
|
||||
" assert_equal(stack.pop(), 5)\n",
|
||||
" assert_equal(stack.peek(), None)\n",
|
||||
"\n",
|
||||
" print('Test: More than one element')\n",
|
||||
" stack = Stack()\n",
|
||||
" stack.push(1)\n",
|
||||
" stack.push(2)\n",
|
||||
" stack.push(3)\n",
|
||||
" assert_equal(stack.pop(), 3)\n",
|
||||
" assert_equal(stack.peek(), 2)\n",
|
||||
" assert_equal(stack.pop(), 2)\n",
|
||||
" assert_equal(stack.peek(), 1)\n",
|
||||
" assert_equal(stack.is_empty(), False)\n",
|
||||
" assert_equal(stack.pop(), 1)\n",
|
||||
" assert_equal(stack.peek(), None)\n",
|
||||
" assert_equal(stack.is_empty(), True)\n",
|
||||
" \n",
|
||||
" print('Success: test_end_to_end')\n",
|
||||
"\n",
|
||||
"if __name__ == '__main__':\n",
|
||||
" test = Test()\n",
|
||||
" test.test_end_to_end()"
|
||||
]
|
||||
},
|
||||
{
|
||||
"cell_type": "markdown",
|
||||
"metadata": {},
|
||||
"source": [
|
||||
"## Pythonic-Code"
|
||||
]
|
||||
},
|
||||
{
|
||||
"cell_type": "markdown",
|
||||
"metadata": {},
|
||||
"source": [
|
||||
"Source: https://docs.python.org/2/tutorial/datastructures.html#using-lists-as-stacks\n",
|
||||
"<pre>\n",
|
||||
"5.1.1. Using Lists as Stacks\n",
|
||||
"The list methods make it very easy to use a list as a stack, where the last element added is the first element retrieved (“last-in, first-out”). To add an item to the top of the stack, use append(). To retrieve an item from the top of the stack, use pop() without an explicit index. For example:\n",
|
||||
"\n",
|
||||
">>> stack = [3, 4, 5]\n",
|
||||
">>> stack.append(6)\n",
|
||||
">>> stack.append(7)\n",
|
||||
">>> stack\n",
|
||||
"[3, 4, 5, 6, 7]\n",
|
||||
">>> stack.pop()\n",
|
||||
"7\n",
|
||||
">>> stack\n",
|
||||
"[3, 4, 5, 6]\n",
|
||||
">>> stack.pop()\n",
|
||||
"6\n",
|
||||
">>> stack.pop()\n",
|
||||
"5\n",
|
||||
">>> stack\n",
|
||||
"[3, 4]\n",
|
||||
"</pre>"
|
||||
]
|
||||
}
|
||||
],
|
||||
"metadata": {
|
||||
"kernelspec": {
|
||||
"display_name": "Python 2",
|
||||
"language": "python",
|
||||
"name": "python2"
|
||||
},
|
||||
"language_info": {
|
||||
"codemirror_mode": {
|
||||
"name": "ipython",
|
||||
"version": 2
|
||||
},
|
||||
"file_extension": ".py",
|
||||
"mimetype": "text/x-python",
|
||||
"name": "python",
|
||||
"nbconvert_exporter": "python",
|
||||
"pygments_lexer": "ipython2",
|
||||
"version": "2.7.10"
|
||||
}
|
||||
},
|
||||
"nbformat": 4,
|
||||
"nbformat_minor": 0
|
||||
}
|
||||
Reference in New Issue
Block a user