bisection/index.js

A JavaScript port of the bisection algorithm that is used in Python

'use strict';

/**
 * Calculates the index of the Array where item X should be placed, assuming the Array is sorted.
 *
 * @param {Array} array The array containing the items.
 * @param {Number} x The item that needs to be added to the array.
 * @param {Number} low Inital Index that is used to start searching, optional.
 * @param {Number} high The maximum Index that is used to stop searching, optional.
 * @returns {Number} the index where item X should be placed
 */
function bisection(array, x, low, high){
  // The low and high bounds the inital slice of the array that needs to be searched
  // this is optional
  low = low || 0;
  high = high || array.length;

  var mid;

  while (low < high) {
    mid = (low + high) >> 1;

    if (x < array[mid]) {
      high = mid;
    } else {
      low = mid + 1;
    }
  }

  return low;
}

/**
 * A right bisection is default, so just reference the same function
 */
bisection.right = bisection;

/**
 * Calculates the index of the Array where item X should be placed, assuming the Array is sorted.
 * @param {Array} array The array containing the items.
 * @param {number} x The item that needs to be added to the array.
 * @param {number} low Inital Index that is used to start searching, optional.
 * @param {number} high The maximum Index that is used to stop searching, optional.
 * @return {number} the index where item X should be placed
 */
bisection.left = function left( array, x, low , high ){
  // The low and high bounds the inital slice of the array that needs to be searched
  // this is optional
  low = low || 0;
  high = high || array.length;

  var mid;

  while (low < high) {
    mid = (low + high) >> 1;

    if (x < array[mid]) {
      low = mid + 1;
    } else {
      high = mid;
    }
  }

  return low;
};

/**
 * Library version
 */
bisection.version = '0.0.3';

module.exports = bisection;