system-design-primer/solutions/object_oriented_design/hash_table/hash_map.ipynb

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2017-03-04 09:53:41 +07:00
{
"cells": [
{
"cell_type": "markdown",
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"source": [
"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-primer)."
]
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{
"cell_type": "markdown",
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"source": [
"# Design a hash map"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Constraints and assumptions\n",
"\n",
"* For simplicity, are the keys integers only?\n",
" * Yes\n",
"* For collision resolution, can we use chaining?\n",
" * Yes\n",
"* Do we have to worry about load factors?\n",
" * No\n",
"* Can we assume inputs are valid or do we have to validate them?\n",
" * Assume they're valid\n",
"* Can we assume this fits memory?\n",
" * Yes"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Solution"
]
},
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"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"Overwriting hash_map.py\n"
]
}
],
"source": [
"%%writefile hash_map.py\n",
"class Item(object):\n",
"\n",
" def __init__(self, key, value):\n",
" self.key = key\n",
" self.value = value\n",
"\n",
"\n",
"class HashTable(object):\n",
"\n",
" def __init__(self, size):\n",
" self.size = size\n",
" self.table = [[] for _ in range(self.size)]\n",
"\n",
" def _hash_function(self, key):\n",
" return key % self.size\n",
"\n",
" def set(self, key, value):\n",
" hash_index = self._hash_function(key)\n",
" for item in self.table[hash_index]:\n",
" if item.key == key:\n",
" item.value = value\n",
" return\n",
" self.table[hash_index].append(Item(key, value))\n",
"\n",
" def get(self, key):\n",
" hash_index = self._hash_function(key)\n",
" for item in self.table[hash_index]:\n",
" if item.key == key:\n",
" return item.value\n",
" raise KeyError('Key not found')\n",
"\n",
" def remove(self, key):\n",
" hash_index = self._hash_function(key)\n",
" for index, item in enumerate(self.table[hash_index]):\n",
" if item.key == key:\n",
" del self.table[hash_index][index]\n",
" return\n",
" raise KeyError('Key not found')"
]
}
],
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