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Commit ec470dc

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Merge pull request #162 from knaxus/bloom-filters
Bloom filters
2 parents d77dbb7 + b3ef051 commit ec470dc

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4 files changed

+184
-6
lines changed

4 files changed

+184
-6
lines changed

β€ŽTOC.md

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- [K Largest Elements](src/_DataStructures_/Heaps/k-largest-in-array)
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- [K Smallest Elements](src/_DataStructures_/Heaps/k-smallest-in-array)
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- [Hash Table](src/_DataStructures_/HashTable)
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- [Set](src/_DataStructures_/Set)
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- [Bloom Filters](src/_DataStructures_/BloomFilters)
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### Logical Problems
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class BloomFilters {
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constructor(size = 101) {
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this.size = size;
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this.data = this.getStorage(size);
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}
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add(element) {
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const indices = this.getIndices(element);
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for (let i = 0; i < indices.length; i += 1) {
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this.data.setBit(indices[i]);
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}
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}
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contains(element) {
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const indices = this.getIndices(element);
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for (let i = 0; i < indices.length; i += 1) {
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const index = indices[i];
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if (!this.data.getBit(index)) {
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return false; // item is definately not there
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}
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}
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return true; // item may be there
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}
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getIndices(element) {
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return [this.hashOne(element), this.hashTwo(element), this.hashThree(element)];
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}
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hashOne(value) {
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const stringValue = String(value);
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let hashVal = 0;
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for (let i = 0; i < stringValue.length; i += 1) {
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hashVal += stringValue.charCodeAt(i) - 96;
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}
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// eslint-disable-next-line no-bitwise
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hashVal &= hashVal;
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return Math.abs(hashVal % this.size);
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}
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hashTwo(value) {
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const stringValue = String(value);
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const PRIME_MULTIPLIER = 1801; // Random prime number
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let hashVal = 0;
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for (let i = 0; i < stringValue.length; i += 1) {
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hashVal += stringValue.charCodeAt(i) - 96;
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hashVal *= PRIME_MULTIPLIER;
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}
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return Math.abs(hashVal % this.size);
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}
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hashThree(value) {
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const stringValue = String(value);
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const PRIME_MULTIPLIER = 1801; // Random prime number
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const PRIME_ADDER = 2029; // Random prime number
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let hashVal = 0;
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for (let i = 0; i < stringValue.length; i += 1) {
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hashVal += stringValue.charCodeAt(i) - 96;
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hashVal *= PRIME_MULTIPLIER;
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hashVal += PRIME_ADDER;
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}
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// eslint-disable-next-line no-bitwise
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hashVal &= hashVal;
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return Math.abs(hashVal % this.size);
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}
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// eslint-disable-next-line class-methods-use-this
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getStorage(size) {
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const data = new Array(size).fill(0);
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return {
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setBit(index) {
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data[index] = 1;
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},
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getBit(index) {
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return data[index];
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},
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};
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}
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}
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// const b = new BloomFilters();
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// b.add('React.js');
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// b.add('Node.js');
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// console.log(b.contains('JavaScript'));
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// console.log(b.contains('React.js'));
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module.exports = BloomFilters;

β€Žsrc/_DataStructures_/HashTable/index.js

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@@ -11,15 +11,15 @@ class HashTable {
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this.threshold = 0.7;
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// the main bucket
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this.bucket = new Array(this.slot);
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// fill the bucket with null
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// for (let i = 0; i < this.slot; i += 1) this.bucket[i] = null;
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this.bucket.fill(null);
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this.allowResize = allowResize;
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this.strongHash = strongHash;
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if (custonHash) {
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// eslint-disable-next-line no-underscore-dangle
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this._hash = custonHash;
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}
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// fill the bucket with null
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for (let i = 0; i < this.slot; i += 1) this.bucket[i] = null;
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}
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_hash(key) {
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for (let i = 0; i < loopTill; i += 1) {
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const char = stringKey[i];
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const value = char.charCodeAt(0) - 96;
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index = (index * PRIME_MULTIPLIER + value) % this.bucket.length;
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// eslint-disable-next-line no-bitwise
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index &= index;
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index = index * PRIME_MULTIPLIER + value;
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if (this.strongHash) {
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index =(index+PRIME_ADDER)%this.bucket.length;
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index +=PRIME_ADDER;
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}
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}
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return index;
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return Math.abs(index%this.bucket.length);
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}
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_resize() {

β€Žsrc/_DataStructures_/Set/index.js

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// XSet because ES6 already has a Set class
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class XSet {
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constructor() {
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this.data = this.getStore();
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}
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add(element) {
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this.data.push(element);
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}
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remove(element) {
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this.data.pop(element);
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}
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has(element) {
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return this.data.contains(element);
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}
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values() {
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return this.data.val();
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}
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union(givenSet) {
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const result = new Set();
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const firstSetValues = this.values();
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const givenSetValues = givenSet.values();
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// eslint-disable-next-line no-restricted-syntax
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for (const e of firstSetValues) result.add(e);
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// eslint-disable-next-line no-restricted-syntax
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for (const e of givenSetValues) result.add(e);
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return result;
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}
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// eslint-disable-next-line class-methods-use-this
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getStore() {
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const store = {};
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return {
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push(el) {
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if (!store[el]) {
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store[el] = true;
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}
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},
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pop(el) {
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if (store[el]) {
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delete store[el];
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}
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},
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contains(el) {
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return !!store[el];
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},
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val() {
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return Object.keys(store);
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},
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};
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}
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}
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// const s = new XSet();
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// s.add(10);
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// s.add(20);
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// s.add(90);
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// console.log(s.has(1));
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// console.log(s.has(10));
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// console.log(s.has(90));
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// console.log(s.values());
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// s.remove(90);
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// console.log(s.has(90));
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// console.log(s.data);
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module.exports = XSet;

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