2019_day_4.aes

include "List.aes"
include "Pair.aes"

contract AdventOfCode2019Day04 =

  entrypoint test() =
    require(true == check_1([1,1,1,1,1,1]), "test 1 failed")
    require(true == check_1([2,2,3,4,5,0]), "test 2 failed")
    require(false == check_1([1,2,3,7,8,9]), "test 3 failed")
    require(true == check_2([1,1,2,2,3,3]), "test 4 failed")
    require(true == check_2([2,4,5,6,6,7]), "test 5 failed")
    require(false == check_2([1,2,3,4,4,4]), "test 6 failed")
    require(true == check_1([1,1,1,1,2,2]), "test 7 failed")
    true

  entrypoint solve_1() =
    switch(input())
      (current, upper) =>
        solve_int(0, current, upper, check_1)

  entrypoint solve_2() =
    switch(input())
      (current, upper) =>
        solve_int(0, current, upper, check_2)

  function solve_int(n, current, upper, check_fun) =
    let n' = if (check_fun(current) == true) n + 1
             else                            n
    if (current == upper)
      n'
    else
      solve_int(n', next(current, upper), upper, check_fun)

  function next(digits : list(int), limit : list(int)) : list(int) =
    if (digits == limit)
      digits
    else
      let res = List.foldr(increment_digits, ([], false, true), digits)
      switch(res)
        (next', _, valid) =>
          if (valid == true) next'
          else               next(next', limit)

  function increment_digits(n : int, acc : (list(int) * bool * bool)) : (list(int) * bool * bool) =
    switch(acc)
      (digits, done, valid) =>
        switch((n, digits, done, valid))
          (_, [], true, _) =>
            ([n], true, valid)
          (_, n0 :: digits, true, _) =>
            (n :: n0 :: digits, true, valid && n =< n0)
          (9, [], _, valid) =>
            ([0], false, valid)
          (9, n0 :: digits, done, valid) =>
            (0 :: n0 :: digits, false, valid && 0 =< n0)
          (_, [], _, valid) =>
            ([n+1], true, valid)
          (_, 9 :: digits, done, valid) =>
            (n+1 :: 9 :: digits, true, valid && (n+1) =< 9)
          (_, n0 :: digits, done, valid) =>
            (n+1 :: n0 :: digits, true, valid && (n+1) =< n0)

  function check_1(digits) =
    let res = List.foldl((acc, n) =>
      switch(acc)
        (n', check) =>
          let check' = check || (n == n')
          (n, check'),
          (-1, false), digits)
    switch(res)
      (_, check) =>
        check

  function check_2(digits) =
    let res = List.foldl((acc, n) =>
      switch(acc)
        (n2, n1, n0, check, l) =>
          if   (l == 1)
            let check' = check || (n == n2 && n2 != n1) || (n2 == n1 && n != n2 && n1 != n0)
            (n, n2, n1, check', 0)
          elif (n0 == -1)
            let check' = check || (n != n2 && n2 == n1)
            (n, n2, n1, check', l-1)
          else
            let check' = check || (n != n2 && n2 == n1 && n1 != n0)
            (n, n2, n1, check', l-1),
            (-1, -2, -2, false, List.length(digits)), digits)
    switch (res)
      (_, _, _, check, _) =>
        check

  function input() =
    ([2,4,0,9,2,0], [7,8,9,8,5,7])