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https://github.com/donnemartin/interactive-coding-challenges
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Add tree lca challenge
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Donne Martin
221
graphs_trees/tree_lca/tree_lca_challenge.ipynb
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graphs_trees/tree_lca/tree_lca_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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"This notebook was prepared by [Donne Martin](https://github.com/donnemartin). Source and license info is on [GitHub](https://github.com/donnemartin/interactive-coding-challenges)."
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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: Find the lowest common ancestor in a binary tree.\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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"* Is this a binary search tree?\n",
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" * No\n",
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"* Can we assume the two nodes are in the tree?\n",
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" * No\n",
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"* Can we assume this fits memory?\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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"<pre>\n",
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" _10_\n",
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" / \\\n",
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" 5 9\n",
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" / \\ / \\\n",
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" 12 3 18 20\n",
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" / \\ /\n",
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" 1 8 40\n",
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"</pre>\n",
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"\n",
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"* 0, 5 -> None\n",
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"* 5, 0 -> None\n",
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"* 1, 8 -> 3\n",
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"* 12, 8 -> 5\n",
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"* 12, 40 -> 10\n",
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"* 9, 20 -> 9\n",
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"* 3, 5 -> 5"
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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](). 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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"class Node(object):\n",
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"\n",
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" def __init__(self, key, left=None, right=None):\n",
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" self.key = key\n",
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" self.left = left\n",
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" self.right = right\n",
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"\n",
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" def __repr__(self):\n",
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" return str(self.key)"
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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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"class BinaryTree(object):\n",
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"\n",
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" def lca(self, root, node1, node2):\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"
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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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"**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_lca.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 TestLowestCommonAncestor(object):\n",
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"\n",
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" def test_lca(self):\n",
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" node10 = Node(10)\n",
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" node5 = Node(5)\n",
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" node12 = Node(12)\n",
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" node3 = Node(3)\n",
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" node1 = Node(1)\n",
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" node8 = Node(8)\n",
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" node9 = Node(9)\n",
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" node18 = Node(18)\n",
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" node20 = Node(20)\n",
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" node40 = Node(40)\n",
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" node3.left = node1\n",
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" node3.right = node8\n",
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" node5.left = node12\n",
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" node5.right = node3\n",
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" node20.left = node40\n",
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" node9.left = node18\n",
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" node9.right = node20\n",
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" node10.left = node5\n",
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" node10.right = node9\n",
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" root = node10\n",
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" node0 = Node(0)\n",
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" binary_tree = BinaryTree()\n",
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" assert_equal(binary_tree.lca(root, node0, node5), None)\n",
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" assert_equal(binary_tree.lca(root, node5, node0), None)\n",
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" assert_equal(binary_tree.lca(root, node1, node8), node3)\n",
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" assert_equal(binary_tree.lca(root, node12, node8), node5)\n",
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" assert_equal(binary_tree.lca(root, node12, node40), node10)\n",
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" assert_equal(binary_tree.lca(root, node9, node20), node9)\n",
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" assert_equal(binary_tree.lca(root, node3, node5), node5)\n",
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" print('Success: test_lca')\n",
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"\n",
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"\n",
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"def main():\n",
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" test = TestLowestCommonAncestor()\n",
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" test.test_lca()\n",
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"\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]() 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 3",
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"language": "python",
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"name": "python3"
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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": 3
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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": "ipython3",
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"version": "3.5.0"
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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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