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// Two Number sum algorithm challenge
// Solution using the algebraic method
 const twoNumberSum = (array, targetSum) => {
	const hashTable = {}
	for (let value of array) {
		let yValue = targetSum - value;
		if (hashTable[yValue]) {
			return [yValue, value]
		}
		else {

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// using the pointer method the three number algorithm is solved
let threeSumArray = (array, targetSum) => {
  array.sort((a, b) => a - b);
  const triplet = []
  for (let i = 0; i < array.length - 2; i++) {
   // initialize the pointers
    let left = i + 1
    let right = array.length - 1
    while (left < right) {
      let currentSum = array[i] + array[left] + array[right]

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function isValidSubsequence(array, sequence) {
  /*
    On getting two non-empty integer arrays, for example [1, 4, 5, 2, 9, 13, 11]
    A second array [4, 2, 11] can be said to be a subsequence of the first one because it contains all the element
    present in the first one in the same order those appear in the first one, even though they are not adjacent.
    
    The algorithm below works by comparing the two array, looping through the first one once and then checking for
    each value if it is equal to the element in the subsequence array, once a match is found, it's on to the next 
    element in the subsequence. Note that if no match is found, the lenght of the subsequence array will never be same
    as the value of variable "Seq"

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An array of integers is defined as being in meandering order when the first two elements are the respective largest and smallest elements in the array and the subsequent elements alternate between its next largest and next smallest elements. In other words, the elements are in order of [first_largest, first_smallest, second_largest, second_smallest, ...].

Example

The array [5, 2, 7, 8, -2, 25, 25] sorted normally is [-2, 2, 5, 7, 8, 25, 25]. Sorted in meandering order, it becomes [25, -2, 25, 2, 8, 5, 7]

Function Description

The function takes one parameter, unsorted[n]: the unsorted array