Added circular array implementation
sarathsp06
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1b339dbdde
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51741b7a96
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@ -0,0 +1,222 @@
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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 [Sarath S Pillai](https://github.com/sarathsp06). Source and license info is on [GitHub](https://github.com/donnemartin/system-design-primer-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 circular array"
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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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"* Can we assume this fits memory?\n",
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" * Yes\n",
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"* Is array size fixed\n",
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" * Yes\n",
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"* What happens to deleted indexes\n",
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" * None onget request"
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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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"## Circular array Interface\n",
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"* \\[idx\\]\n",
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" * get item on idx ,assuming circular array\n",
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" * any idx value is taken as modulo of itself with size\n",
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" * negative idx is not permitted\n",
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"* len\n",
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" * length is always length of current valid entries\n",
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"* repr\n",
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" * the circular aray is printed with values in order\n",
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" * logical order is maintained not how it is stored\n",
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"* push\n",
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" * pushed item to end of queue\n",
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" * throws exception if capcity is filled , len == capcaity\n",
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"* pop\n",
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" * pop an item from start of array\n",
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" * throws exception if \n",
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"* capacity\n",
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" * returns initial size of array "
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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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"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 circular_array.py\n"
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]
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}
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],
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"source": [
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"%%writefile circular_array.py\n",
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"class CircularArray(object):\n",
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" def __init__(self, size):\n",
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" if size <= 0:\n",
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" raise ValueError(\"Size has to be non zero positive number\")\n",
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" self.size = size\n",
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" self.array = self.size *[None]\n",
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" self.start = self.end = None\n",
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" \n",
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" def capacity(self):\n",
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" return self.size\n",
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" \n",
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" def __len__(self):\n",
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" if self.start is None:\n",
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" return 0\n",
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" return (self.end - self.start + self.size ) % self.size + 1\n",
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" \n",
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" def __getitem__(self, key):\n",
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" if key < 0:\n",
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" raise ValueError(\"Key has to be a positive number\")\n",
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" if self.start is None:\n",
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" return None\n",
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" index = (key + self.start) % self.size\n",
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" return self.array[index]\n",
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" \n",
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" def push(self, value):\n",
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" if self.start is None:\n",
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" self.start = self.end = 0\n",
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" else:\n",
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" index = (self.end + 1) % self.size\n",
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" if index == self.start:\n",
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" raise IndexError(\"Push to full array \")\n",
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" self.end = index\n",
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" self.array[self.end] = value\n",
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" \n",
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" def __repr__(self):\n",
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" if self.start is None:\n",
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" return '[]'\n",
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" if self.start < self.end:\n",
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" return repr(self.array[self.start:self.end+1])\n",
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" return repr(self.array[self.start:]+self.array[:self.end+1])\n",
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" \n",
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" def pop(self):\n",
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" if self.start is None:\n",
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" raise RuntimeException(\"Pop on nil array\")\n",
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" value = self.array[self.start]\n",
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" if self.start == self.end:\n",
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" self.start = self.end = None\n",
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" return value\n",
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" self.start = (self.start + 1) % self.size\n",
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" return value"
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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\n",
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"\n",
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"Here are basic test cases to illustrate the features"
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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": 8,
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"metadata": {},
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"outputs": [],
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"source": [
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"from circular_array import CircularArray\n",
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"# create a circular array of 10 elements\n",
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"ca = CircularArray(10);\n",
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"assert ca.capacity() == 10\n",
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"\n",
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"#push 4 items\n",
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"ca.push(1)\n",
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"ca.push(2)\n",
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"ca.push(3)\n",
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"ca.push(4)\n",
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"assert ca.capacity() == 10\n",
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"\n",
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"#pop and check 3 elements\n",
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"assert ca.pop() == 1\n",
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"assert ca.pop() == 2\n",
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"assert ca.pop() == 3\n",
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"assert len(ca) == 1\n",
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"\n",
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"#push 4 more elements\n",
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"ca.push(5)\n",
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"ca.push(6)\n",
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"ca.push(7)\n",
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"ca.push(8)\n",
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"assert len(ca) == 5\n",
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"\n",
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"#check getitem function for proper indexing and pop 2 elements\n",
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"assert ca[0] == 4\n",
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"assert ca.pop() == 4\n",
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"assert ca[0] == 5\n",
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"assert ca[10] == 5\n",
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"assert ca.pop() == 5\n",
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"assert len(ca) == 3\n",
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"#push 7 more items \n",
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"ca.push(9)\n",
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"ca.push(10)\n",
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"ca.push(11)\n",
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"ca.push(12)\n",
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"ca.push(13)\n",
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"ca.push(14)\n",
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"ca.push(15)\n",
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"assert len(ca) == 10\n",
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"assert ca.capacity() == 10\n",
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"assert repr(ca) == '[6, 7, 8, 9, 10, 11, 12, 13, 14, 15]'\n",
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"assert ca[1] == 7\n",
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"assert ca[11] == 7"
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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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"outputs": [],
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"source": []
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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": "3.6.3"
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}
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},
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"nbformat": 4,
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"nbformat_minor": 1
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}
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@ -0,0 +1,50 @@
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class CircularArray(object):
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def __init__(self, size):
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if size <= 0:
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raise ValueError("Size has to be non zero positive number")
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self.size = size
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self.array = self.size *[None]
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self.start = self.end = None
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def capacity(self):
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return self.size
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def __len__(self):
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if self.start is None:
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return 0
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return (self.end - self.start + self.size ) % self.size + 1
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def __getitem__(self, key):
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if key < 0:
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raise ValueError("Key has to be a positive number")
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if self.start is None:
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return None
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index = (key + self.start) % self.size
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return self.array[index]
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def push(self, value):
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if self.start is None:
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self.start = self.end = 0
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else:
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index = (self.end + 1) % self.size
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if index == self.start:
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raise IndexError("Push to full array ")
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self.end = index
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self.array[self.end] = value
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def __repr__(self):
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if self.start is None:
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return '[]'
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if self.start < self.end:
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return repr(self.array[self.start:self.end+1])
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return repr(self.array[self.start:]+self.array[:self.end+1])
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def pop(self):
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if self.start is None:
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raise RuntimeException("Pop on nil array")
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value = self.array[self.start]
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if self.start == self.end:
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self.start = self.end = None
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return value
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self.start = (self.start + 1) % self.size
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return value
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