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https://github.com/donnemartin/interactive-coding-challenges
synced 2026-01-13 12:58:02 +00:00
Added stack min challenge.
This commit is contained in:
Donne Martin
208
stacks_queues/stack_min/stack_min_challenge.ipynb
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208
stacks_queues/stack_min/stack_min_challenge.ipynb
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{
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"cells": [
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"<small><i>This notebook was prepared by [Donne Martin](http://donnemartin.com). Source and license info is on [GitHub](https://github.com/donnemartin/coding-challenges).</i></small>"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"# Challenge Notebook"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Problem: Implement a stack with push, pop, and min methods running O(1) time.\n",
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"\n",
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"* [Constraints](#Constraints)\n",
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"* [Test Cases](#Test-Cases)\n",
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"* [Algorithm](#Algorithm)\n",
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"* [Code](#Code)\n",
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"* [Unit Test](#Unit-Test)\n",
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"* [Solution Notebook](#Solution-Notebook)"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Constraints\n",
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"\n",
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"*Problem statements are sometimes ambiguous. Identifying constraints and stating assumptions can help to ensure you code the intended solution.*\n",
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"\n",
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"* Can we assume this is a stack of ints?\n",
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" * Yes\n",
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"* If we call this function on an empty stack, can we return max int?\n",
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" * Yes\n",
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"* Can we assume we already have a stack class that can be used for this problem?\n",
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" * Yes"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Test Cases\n",
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"\n",
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"* Push/pop on empty stack\n",
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"* Push/pop on non-empty stack"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Algorithm\n",
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"\n",
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"Refer to the [Solution Notebook](http://nbviewer.ipython.org/github/donnemartin/coding-challenges/blob/master/stacks_queues/stack_min/stack_min_solution.ipynb). If you are stuck and need a hint, the solution notebook's algorithm discussion might be a good place to start."
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Code"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {
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"collapsed": true
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},
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"outputs": [],
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"source": [
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"%run ../stack/stack.py\n",
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"%load ../stack/stack.py"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {
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"collapsed": true
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},
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"outputs": [],
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"source": [
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"import sys\n",
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"\n",
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"\n",
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"class MyStack(Stack):\n",
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" def __init__(self, top=None):\n",
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" # TODO: Implement me\n",
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" pass\n",
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"\n",
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" def min(self):\n",
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" # TODO: Implement me\n",
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" pass\n",
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"\n",
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" def push(self, data):\n",
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" # TODO: Implement me\n",
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" pass\n",
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"\n",
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" def pop(self):\n",
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" # TODO: Implement me\n",
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" pass"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Unit Test\n",
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"\n",
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"\n",
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"\n",
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"**The following unit test is expected to fail until you solve the challenge.**"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {
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"collapsed": false
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},
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"outputs": [],
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"source": [
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"# %load test_stack_min.py\n",
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"from nose.tools import assert_equal\n",
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"\n",
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"\n",
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"class TestStackMin(object):\n",
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" def test_stack_min(self):\n",
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" print('Test: Push on empty stack, non-empty stack')\n",
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" stack = MyStack()\n",
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" stack.push(5)\n",
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" assert_equal(stack.peek(), 5)\n",
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" assert_equal(stack.min(), 5)\n",
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" stack.push(1)\n",
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" assert_equal(stack.peek(), 1)\n",
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" assert_equal(stack.min(), 1)\n",
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" stack.push(3)\n",
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" assert_equal(stack.peek(), 3)\n",
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" assert_equal(stack.min(), 1)\n",
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" stack.push(0)\n",
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" assert_equal(stack.peek(), 0)\n",
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" assert_equal(stack.min(), 0)\n",
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"\n",
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" print('Test: Pop on non-empty stack')\n",
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" assert_equal(stack.pop(), 0)\n",
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" assert_equal(stack.min(), 1)\n",
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" assert_equal(stack.pop(), 3)\n",
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" assert_equal(stack.min(), 1)\n",
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" assert_equal(stack.pop(), 1)\n",
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" assert_equal(stack.min(), 5)\n",
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" assert_equal(stack.pop(), 5)\n",
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" assert_equal(stack.min(), sys.maxint)\n",
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"\n",
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" print('Test: Pop empty stack')\n",
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" assert_equal(stack.pop(), None)\n",
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" \n",
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" print('Success: test_stack_min')\n",
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"\n",
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"def main():\n",
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" test = TestStackMin()\n",
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" test.test_stack_min()\n",
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"\n",
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"if __name__ == '__main__':\n",
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" main()"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Solution Notebook\n",
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"\n",
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"Review the [Solution Notebook](http://nbviewer.ipython.org/github/donnemartin/coding-challenges/blob/master/stacks_queues/stack_min/stack_min_solution.ipynb) for a discussion on algorithms and code solutions."
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]
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}
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],
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"metadata": {
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"kernelspec": {
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"display_name": "Python 2",
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"language": "python",
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"name": "python2"
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},
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"language_info": {
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"codemirror_mode": {
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"name": "ipython",
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"version": 2
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},
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"file_extension": ".py",
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"mimetype": "text/x-python",
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"name": "python",
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"nbconvert_exporter": "python",
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"pygments_lexer": "ipython2",
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"version": "2.7.10"
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}
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},
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"nbformat": 4,
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"nbformat_minor": 0
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}
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