gistfile1.txt

const balancedSum = (arr) => {
  // Find the left and right parts of the array, start from the middle cos it's as good a place as any
  let i = Math.floor(arr.length / 2)
  let left = arr.slice(0, i).reduce((a, b) => a + b, 0)
  let right = arr.slice(i + 1).reduce((a, b) => a + b, 0)

  // If they're equal, you beauty
  if (left === right) {
    return i
  }

  // We can compare them. We know the array is sorted...
  // so we know that if left < right, we need to remove the first item from right and add to left
  // and vice-versa. We can also assume there will always be a solution so....
  let iterations = 0
  while (left !== right) {
    iterations += 1
    if (left < right) {
      // Add to the left, remove from the right
      left += arr[i]
      right -= arr[i + 1]

      // Increment the index
      i += 1
    } else {
      // Add to the right, remove from the left
      right += arr[i]
      left -= arr[i - 1]

      // Decrement the index
      i -= 1
    }
  }

  console.log(`${iterations} iteration(s)`)
  return i
}

console.log(balancedSum([1, 2, 3, 4, 6]))