MaxProductOfThree.js

/**
 * Given an array of numbers, return the maximum product
 * of 3 numbers from the array
 * https://wsvincent.com/javascript-three-sum-highest-product-of-three-numbers/
 * @param {number[]} arrayItems
 * @returns number
 */
export function maxProductOfThree(arrayItems) {
 // if size is less than 3, no triplet exists
 const n = arrayItems.length
 if (n < 3) throw new Error('Triplet cannot exist with the given array')
 let max1 = arrayItems[0]
 let max2 = null
 let max3 = null
 let min1 = arrayItems[0]
 let min2 = null
 for (let i = 1; i < n; i++) {
 if (arrayItems[i] > max1) {
 max3 = max2
 max2 = max1
 max1 = arrayItems[i]
 } else if (max2 === null || arrayItems[i] > max2) {
 max3 = max2
 max2 = arrayItems[i]
 } else if (max3 === null || arrayItems[i] > max3) {
 max3 = arrayItems[i]
 }
 if (arrayItems[i] < min1) {
 min2 = min1
 min1 = arrayItems[i]
 } else if (min2 === null || arrayItems[i] < min2) {
 min2 = arrayItems[i]
 }
 }
 const prod1 = max1 * max2 * max3
 const prod2 = max1 * min1 * min2
 return Math.max(prod1, prod2)
}