• Description
• Recursive Heap's algorithm with callback in place
• Recursive Heap's algorithm with returning value
• Iterative Heap's algorithm with callback in place
• Iterative Heap's algorithm with returning value

Description

This project implements 4 different variations of the heap's algorithm for finding all the permutations of a certain array.

Recursive Heap's algorithm with callback in place

The following uses a recursive variation of the heap's algorithm.
In this implementation the function calcRecursiveAllPermutationsInPlace calculates every possible permutation of the array parameter and execute the callback passing a reference of the active permutation.
It is important to notice that if one want to use this permutation the array need to be spreadded because the array is changed in place.
This is wanted because one could potentially use this fn for write the permutation to a file, in this way unnecessary spreads are avoided.
If one want to have an array of all the possible permutations, another one of these methods could be used.

const {calcRecursiveAllPermutationsInPlace} = require("./index");

const result = [];
calcRecursiveAllPermutationsInPlace([1, 2, 3], (permutation) => {
  // create optionally another arr was chosen for performance
  // one could optionally decide to not add the permutation to the array
  // because maybe one want just to write in a file
  result.push([...permutation]);
});

Then result will be:

[ [1, 2, 3], [2, 1, 3], [3, 1, 2], [1, 3, 2], [2, 3, 1], [3, 2, 1] ]

Recursive Heap's algorithm with returning value

The following uses a recursive variation of the heap's algorithm.
In this implementation the function calcRecursiveAllPermutations calculates every possible permutation of the array parameter and return an array containing all the possible permutations.
In this case the array passed as a parameter won't change during the process, also the permutation that is equal to the passed parameter is a totally different array.

const {calcRecursiveAllPermutations} = require("./index");

const result = calcRecursiveAllPermutations([1, 2, 3]);

Then result will be:

[ [1, 2, 3], [2, 1, 3], [3, 1, 2], [1, 3, 2], [2, 3, 1], [3, 2, 1] ]

Iterative Heap's algorithm with callback in place

The following uses an iterative variation of the heap's algorithm.
In this implementation the function calcIterativeAllPermutationsInPlace calculates every possible permutation of the array parameter and execute the callback passing a reference of the active permutation.
It is important to notice that if one want to use this permutation the array need to be spreadded because the array is changed in place.
This is wanted because one could potentially use this fn for write the permutation to a file, in this way unnecessary spreads are avoided.
If one want to have an array of all the possible permutations, another one of these methods could be used.

const {calcIterativeAllPermutationsInPlace} = require("./index");

const result = [];
calcIterativeAllPermutationsInPlace([1, 2, 3], (permutation) => {
  // create optionally another arr was chosen for performance
  // one could optionally decide to not add the permutation to the array
  // because maybe one want just to write in a file
  result.push([...permutation]);
});

Then result will be:

[ [1, 2, 3], [2, 1, 3], [3, 1, 2], [1, 3, 2], [2, 3, 1], [3, 2, 1] ]

Iterative Heap's algorithm with returning value

The following uses an iterative variation of the heap's algorithm.
In this implementation the function calcIterativeAllPermutations calculates every possible permutation of the array parameter and return an array containing all the possible permutations.
In this case the array passed as a parameter won't change during the process, also the permutation that is equal to the passed parameter is a totally different array.

const {calcIterativeAllPermutations} = require("./index");

const result = calcIterativeAllPermutations([1, 2, 3]);

Then result will be:

[ [1, 2, 3], [2, 1, 3], [3, 1, 2], [1, 3, 2], [2, 3, 1], [3, 2, 1] ]