Following are various implementation of Set Theory - Node.js Data Structure

Node.js examples for Data Structure:Set

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Description

Following are various implementation of Set Theory

Demo Code


/* =============================================================================================================
 * Following are various implementation of Set Theory (http://en.wikipedia.org/wiki/Set_theory#Basic_concepts)
 * /* w w w  .j  a v a 2 s  .co  m*/
 * @source = src= https://code.google.com/p/javascriptsets/downloads/detail?name=array.sets.0.1.js&can=2&q=
 */
//Array.prototype.cartesian = function(a) {
//  var temp = [];
//  for (var i = 0; i < this.length; i++) {
//    for (var j = 0; j < a.length; j++) {
//      temp.push([this[i], a[j]]);
//    }
//  }
//
//  return temp;
//};      
//Array.prototype.complement = function(a) {
//  var keys = {};
//  var temp = [];
//  for (var i = 0; i < a.length; i++) {
//    if (a[i] !== undefined)
//      keys[a[i]] = 1;
//  }
//  for (var i = 0; i < this.length; i++) {
//    if (this[i] !== undefined && keys[this[i]] != undefined) {
//      keys[this[i]]--;
//    }
//  }
//  for (var key in keys) {
//    if (keys[key] > 0) {
//      temp.push(key);
//    }
//  }
//
//  return temp;
//};
//Array.prototype.difference = function(a) {
//  var temp = [];
//  var keys = {};
//  for (var i = 0; i < this.length; i++) {
//    if (this[i] !== undefined)
//      keys[this[i]] = 0;
//  }
//  for (var i = 0; i < a.length; i++) {
//    if (a[i] !== undefined)
//      keys[a[i]] = ++keys[a[i]] || 0; 
//  }
//  for (var key in keys) {
//    if (keys[key] === 0) {
//      temp.push(key);
//    }
//  }
//  return temp;
//};
//Array.prototype.intersection = function(a) {
//  var keys = {};
//  var temp = [];
//  var bigger = (this.length > a.length) ? this : a;
//  var smaller = (this.length > a.length) ? a : this;
//  for (var i = 0; i < smaller.length; i++) {
//    if (smaller[i] !== undefined)
//      keys[smaller[i]] = 1;
//  }
//  for (var i = 0; i < bigger.length; i++) {
//    if (bigger[i] !== undefined && keys[bigger[i]] !== undefined) {
//      keys[bigger[i]]++;
//    }
//  }
//  for (var key in keys) {
//    if (keys[key] === 2) {
//      temp.push(key);
//    }
//  }
//  return temp;
//};
//Array.prototype.powerset = function() {
//  // [x,y,z] => [[],[x],[y],[z],[x,y],[x,z],[y,z],[x,y,z]]
//  var temp = [];
//  var clone = [];
//  // iteration 0 - just add the empty set
//  temp.push([]);
//  // iteration 1 - add each individual element
//  for (var i = 0; i < this.length; i++) {
//    temp.push([this[i]]);
//  }
//  // iteration 2 - add each individual element, unioned with every other element
//  var clone = this.union([]);
//  while (clone.length > 0) {
//    var el = clone[0];
//    var others = clone.complement([el]);
//    for (var i = 0; i < others.length; i++) {
//      temp.push([el, others[i]]);
//    }
//    clone = others;
//  }
//  for (var i = 0; i < this.length; i++) {
//    // hmmmmmm, not quite....
//  }
//  // iteration 3 - add the original set
//  temp.push(this.union([]));
//  return temp;
//};
Array.prototype.union = function(a) {
  var keys = {};
  var temp = [];
  var bigger = (this.length > a.length) ? this : a;
  var smaller = (this.length > a.length) ? a : this;
  // build has table with smaller array
  for (var i = 0; i < smaller.length; i++) {
    if (smaller[i] !== undefined)
      keys[smaller[i]] = 1;
  }
  // loop over larger array checking hash table for matches
  for (var i = 0; i < bigger.length; i++) {
    if (bigger[i] !== undefined) {
      keys[bigger[i]] = 1;
    }
    
  }
  // convert hash table to array and return
  for (var key in keys) {
    temp.push(key);
  }

  return temp;
};
/* 
 * end of SET THEORY
 /* =============================================================================================================
 */

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