Advent of Code, 2017 Day 1 (1/2)

captcha.re

let explode = (input) =>
  Js.String.split("", input)
  |> Array.map(int_of_string)
  |> Array.to_list;

let rec solver = (current, next, rest, first, total) =>
  switch (next == first, current == next, rest) {
  /* when we're on the last item in the list */
  | (true, true, []) => total + current + next
  | (false, true, []) => total + current
  | (true, false, []) => total + next
  | (false, false, []) => total
  /* when we have more to go */
  | (_, true, [next', ...rest']) => solver(next, next', rest', first, total + current)
  | (_, false, [next', ...rest']) => solver(next, next', rest', first, total)
  };

let solve = (input) =>
  switch (explode(input)) {
  | [current, next, ...rest] => solver(current, next, rest, current, 0)
  | _ => 0
  };

/*
 // solution translated to JS; will not work on biiiig numbers D:

 const explode =
  (input) => input.split("").map((s) => parseInt(s, 10));

 const solver = (current, next, rest, first, total) {
   if (rest.length < 1) {
     if (current === next && next === first) {
       return total + current + next;
     }
     else if (current === next) {
       return total + current;
     }
     else if (next === first) {
       return total + next;
     }
     else {
       return total;
     }
   } else {
     const [next1, ...rest1] = rest;
     if (current === next) {
       return solver(next, next1, rest1, first, total + current);
     } else {
       return solver(next, next1, rest1, first, total);
     }

   }
 };

 const solve = (input) => {
   if (input.length < 2) {
     return 0;
   } else {
     const [current, next, ...rest] = explode(input);
     return solver(current, next, rest, current, 0);
   }
 };
  */