Nodejs Array Max Sub Array maxSubArray()

Method Source Code

'use strict';//from   w w w  . j  a va2  s .  c  o m

/**
 * Find the maximum possible sum of a contiguous subarray
 * Implementation based on Kadane's algorithm:
 * https://en.wikipedia.org/wiki/Maximum_subarray_problem
 * @returns {Number}
 */
Array.prototype.maxSubArray = function() {
  let maxToIndex = null;
  let currentMax = null;
  let maxElement = null;

  this.forEach((element) => {
    maxToIndex = Math.max(0, maxToIndex + element);
    currentMax = Math.max(currentMax, maxToIndex);
    maxElement = maxElement == null || element > maxElement ? element : maxElement;
  });
  
  return currentMax > 0 ? currentMax : maxElement;
};

Related

1. maxSubArray()

   'use strict';
   Array.prototype.maxSubArray = Array.prototype.maxSubArray || function () {
     let maxToIndex = null;
     let currentMax = null;
     let maxElement = null;
     this.forEach(element => {
       maxToIndex = Math.max(0, maxToIndex + element);
       currentMax = Math.max(currentMax, maxToIndex);
       maxElement = maxElement === null || element > maxElement ? element : maxElement;
   ...
   

2. maxSubArrayNonContigious()

   Array.prototype.maxSubArrayNonContigious = function() {
     let maxElement = null;
     let sum = null;
     this.forEach((element) => {
       maxElement = maxElement == null || element > maxElement ? element : maxElement;
       sum += element > 0 ? element : 0;
     });
     return sum > 0 ? sum : maxElement;
   };
   ...
   

3. maxSubArrayNonContigious()

   Array.prototype.maxSubArrayNonContigious = Array.prototype.maxSubArrayNonContigious || function () {
     let maxElement = null;
     let sum = null;
     this.forEach(element => {
       maxElement = maxElement === null || element > maxElement ? element : maxElement;
       sum += element > 0 ? element : 0;
     });
     return sum > 0 ? sum : maxElement;
   };
   ...