Hash table class with testing code - Node.js Data Structure

Node.js examples for Data Structure:Hash Table

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Description

Hash table class with testing code

Demo Code


var Hash = function() {
  this.array = [];//from   w w  w.  ja v  a  2  s  .c o m
  this.max_size = 2;
  this.size = 0;
};

var hashCode = function(str) {
  return (""+str).split("").reduce(function(acc,ch,i) {
    return acc+(i+1)*ch.charCodeAt(0);
  }, 0);
};

Hash.prototype.index = function(hash) {
  return hash % this.max_size;
};

var chain = {
  set: function(key, val) {
    var hash  = hashCode(key),
      index = this.index(hash),
      node;

    if (this.array[index]==null) {
      this.size += 1;
      if (this.size > this.max_size*0.8) {
        this.rehash();
      }
      // Recompute index after rehash
      index = this.index(hash);      
      this.array[index] = {key: key, val: val, next: null};
      return;
    }
    node = this.array[index];
    if (node.key==key) { node.val = val; return; }

    while (node.next!=null) {
      node = node.next;
      if (node.key==key) { node.val = val; return; }
    }
    this.size += 1;
    node.next = {key: key, val: val, next: null};    
  },
  get: function(key) {
    var hash = hashCode(key), index, node;
    index = this.index(hash);
    node = this.array[index];
    if (node==null) { return null; }
    while (node.key!=key) {
      node = node.next;
      if (node==null) { return null; }
    }
    return node.val;
  },
  rehash: function() {
    var data = [];
    this.array.forEach(function(v,i) {
      var node = v;
      if (node!=null) { data.push(node); }
      else { return; }

      while (node.next!=null) {
        node = node.next;
        data.push(node);
      }
    }, this);

    this.array = [];
    this.max_size *= 2;
    this.size = 0;
    data.forEach(function(node) {
      this.set(node.key, node.val);
    }, this);
  }
}

Hash.prototype.set = chain.set;
Hash.prototype.get = chain.get;
Hash.prototype.rehash = chain.rehash;

var hash = new Hash();
hash.set("abc", 10);
hash.set("def", 11);
hash.set("asdf", 12);
hash.set("fda", 13);
hash.set("qer", 14);
hash.set("fgh", 15);
hash.set("twre", 16);
hash.set("ijk", 16);
hash.set("lmn", 16);
hash.set("opq", 16);
hash.set("rst", 16);

console.log(hash.get("xyz"));
console.log(hash.get("fgh"));

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