Problem

Given a list of integers, write a recursive function to find the sum of all the integers in the list.
Example input: [1, 2, 3, 4, 5]
Example output: 15

Solution

// Solution:

function sum(arr) {
  if (arr.length === 0) {
    return 0;
  }
  return arr[0] + sum(arr.slice(1));
}

// This solution is optimal because it is a linear solution. It is linear because the number of operations is directly proportional to the size of the input.