targetSum.js

targetSum.js

// define a function 'targetSum' that takes 2 arguments, an array and a target number, and returns a boolean for whether or not 
//2 values in the array sum up to the target number
// ex: targetSum([1, 3, 5, 0, 6, 4, 2], 11) // => 11

// brute force 
function targetSum (arr, target) {
  for (var i = 0; i < arr.length; i++) {
    for (var j = i + 1; j < arr.length; j++) {
      if (arr[i] + arr[j] === target) return true
    }
  }
}

// O(n) time and space, use an object
const target = (arr, target) => {
  const table = {}
  let hasTarget = false
  arr.forEach((n) => table[target - n] 
    ? hasTarget = true 
    : table[n] = 1
  )
  return hasTarget
}