cross-add

cross-add

function crossAdd(input) {
  let answer = [];
  for (let i = 0; i < input.length; i += 1) {
    let goingUp = input[i];
    let goingDown = input(input.length-1-i];
    answer.push(goingUp + goingDown);
  }
  return answer;
}

// input [1, 2, 3]
// output [4, 4, 4]