122 lines
3.0 KiB
Python
122 lines
3.0 KiB
Python
{
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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/system-design-primer)."
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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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"# Design a hash map"
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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 and assumptions\n",
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"\n",
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"* For simplicity, are the keys integers only?\n",
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" * Yes\n",
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"* For collision resolution, can we use chaining?\n",
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" * Yes\n",
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"* Do we have to worry about load factors?\n",
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" * No\n",
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"* Can we assume inputs are valid or do we have to validate them?\n",
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" * Assume they're valid\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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"## Solution"
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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": 1,
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"metadata": {
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"collapsed": false
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},
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"outputs": [
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{
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"name": "stdout",
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"output_type": "stream",
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"text": [
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"Overwriting hash_map.py\n"
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]
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}
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],
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"source": [
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"%%writefile hash_map.py\n",
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"class Item(object):\n",
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"\n",
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" def __init__(self, key, value):\n",
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" self.key = key\n",
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" self.value = value\n",
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"\n",
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"\n",
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"class HashTable(object):\n",
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"\n",
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" def __init__(self, size):\n",
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" self.size = size\n",
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" self.table = [[] for _ in range(self.size)]\n",
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"\n",
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" def _hash_function(self, key):\n",
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" return key % self.size\n",
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"\n",
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" def set(self, key, value):\n",
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" hash_index = self._hash_function(key)\n",
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" for item in self.table[hash_index]:\n",
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" if item.key == key:\n",
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" item.value = value\n",
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" return\n",
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" self.table[hash_index].append(Item(key, value))\n",
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"\n",
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" def get(self, key):\n",
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" hash_index = self._hash_function(key)\n",
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" for item in self.table[hash_index]:\n",
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" if item.key == key:\n",
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" return item.value\n",
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" raise KeyError('Key not found')\n",
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"\n",
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" def remove(self, key):\n",
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" hash_index = self._hash_function(key)\n",
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" for index, item in enumerate(self.table[hash_index]):\n",
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" if item.key == key:\n",
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" del self.table[hash_index][index]\n",
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" return\n",
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" raise KeyError('Key not found')"
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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": "3.4.3"
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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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