Nodejs Array Search Binary binarySearch(n)

Method Source Code

"use strict";/*from   ww w. j  ava2  s  .  co  m*/

var assert = require('assert'); 

Array.prototype.binarySearch = function(n) {

  var O = Object(this);

  var f = function(lo,hi) {
    var mid = Math.floor((lo + hi) / 2);
    if (O[mid] === n) {
      return mid;
    } 

    if (lo === mid || hi === mid) {
      return -(mid+1);
    }

    if(O[mid] < n) {
      return f(mid,hi);
    }

    if (O[mid] > n) {
      return f(lo,mid);
    }
  };

  return f(0, O.length);
};

describe('binary search', function() {
  it('doesnt find anything in an empty list', function() {
    assert.equal(-1, [].binarySearch(7));
  });

  it('finds a single element', function() {
    assert.equal(0, [0].binarySearch(0));
  });

  it('finds the middle element', function() {
    assert.equal(1, [1,2,3].binarySearch(2));
  });

  it('finds up', function() {
    assert.equal(2, [1,2,3].binarySearch(3));
  });

  it('finds down', function() {
    assert.equal(0, [1,2,3].binarySearch(1));
  });

  it('finds insertion index', function() {
    assert.equal(-2, [1,2,4,5,6].binarySearch(3));
  });
});

Related

1. binSearch(data)

   Array.prototype.binSearch = function(data) {
     var first = 0;
     var last = this.length - 1;
     while(first <= last) {
       var mid = Math.floor((first + last) / 2);
       if(this[mid] < data) {
         first = mid + 1;
       else if(this[mid] > data) {
   ...
   

2. binaryIndexOf(searchElement)

   function binaryIndexOf(){
   Array.prototype.binaryIndexOf = function(searchElement) {
       var minIndex = 0;
       var maxIndex = this.length - 1;
       var currentIndex;
       var currentElement;
       while (minIndex <= maxIndex) {
           currentIndex = Math.floor((minIndex + maxIndex) / 2);
           currentElement = this[currentIndex];
   ...
   

3. binaryIndexOfbinaryIndexOf;

   function binaryIndexOf(searchElement, map) {
     'use strict';
     if (map === undefined) map = index => this[index]
     var minIndex = 0;
     var maxIndex = this.length - 1;
     var currentIndex;
     var currentElement;
     var resultIndex;
     while (minIndex <= maxIndex) {
   ...
   

4. binarySearch(num)

   var input = [ 1, 2, 2, 3, 4, 4, 5, 6, 8, 10 ];
   Array.prototype.binarySearch = function(num) {
       var _this = this;
       function search(left, right) {
           if(right < left) return -1;
           else if(left === right) {
               return checkIndexForNum(left);
           var mid = Math.floor((left + right) / 2);
   ...
   

5. binarySearch(searchElement)

   Array.prototype.binarySearch = function (searchElement) {
       'use strict';
       var minIndex = 0;
       var maxIndex = this.length - 1;
       var currentIndex;
       var currentElement;
       while (minIndex <= maxIndex) {
           currentIndex = (minIndex + maxIndex) / 2 | 0;
           currentElement = this[currentIndex];
   ...
   

6. binarySearch(val)

   Array.prototype.binarySearch = function(val){
     var min = 0;
     var max = this.length -1;
     var currentIndex;
     var currentElement;
     while (min <= max) {
       currentIndex = Math.floor((min +max) / 2);
       currentElement = this[currentIndex];
       if (currentElement > val) {
   ...
   

7. binarySearch(val)

   Array.prototype.binarySearch = function(val){
     var keeper = 0;
     var answer = -1;
     function recursive(arr){
       var len = arr.length;
       var start = Math.floor(len / 2);
       var current = arr[start];
       if (current === val){
         answer = start + keeper;
   ...