advent-2016-day2.ps1

#$input = "ULL
#RRDDD
#LURDL
#UUUUD" # Test input, result should be 1985

$input = "LLULLLRLDLLLRLUURDDLRDLDURULRLUULUDDUDDLLLURRLDRRLDRRRLDUDLRDLRRDLLDUDUDUDRLUDUUDLLLRDURUDUULUDLRDUUUDUUDURLDUULLRDLULDUURUDRDDLDRLURLRURRDUURLRLUURURUUULLRLLULRUURLULURDLLRRUDLUDULDRDRLRULUURRDRULLRUUUDLRLDLUURRRURDLUDDRRUDRLUDRDLLLLLRULLDUDRLRRDDULDLRUURRRRRLDLDLRDURDRUUURDLRDDDDULURRRRDUURLULLLDLRULRDULRUDLRRLRDLLRLLLUDDLRDRURDDLLLLDUDRDLRURRDLRDDDLDULDRLRULUUDRRRUUULLLURRDDUULURULDURRLLULLDRURUUULRLRDRRUDRDRRDURRUUUULDRDDDUDLDDURLLRR
LDLRRRUURDLDDRLRRDLLULRULLLUDUUDUDLRULLDRUDRULLDULURDRDDLRURDDULLLLDLRDRDRDDURLURLURLUDRDDRDULULUDDRURRDLLDUURDRDDLRLLURRDLRDDULDLULURDRDLUDRRUUDULLULURRDUDRUUUDRULDLDURLRRUDURLDLRRUURRRURDLUDRLDUDRRUDUURURUDDUUDRDULRDLUDRRRLDRURLLRDDDLUDRDUDURDDDRRDDRRRLLRRDDLDDLRUURRURDLLDRLRRDLLUDRRRURURLRDRLLRLRLRULLRURLDLRRULLRRRDULUUULDRDLLURDDLDLRDRLUUDLLUDDLDRRLDLRUDRUDLLUURLLULURUDUDRLULLUDRURDDLDLDDUDLRDDRRURLRLLUDDUDRUURRURRULDRLDDRLLRRLDDURRDLDULLLURULLLRUURLRRRRUUULRLLLURRLRLRUDRDUUUDUUUDDLULLDLLLLDLDRULDRUUULDDDLURLDLRLULRUDDDDURDDLU
RURLURRDLDULLULDDDLRUULLUURLRUDRUDRRUDDLDDDDRRDLRURLRURLDDDUDDUURRDRULDRRRULRDRDDLRUDULRLURDUUDRRLDLRDRURDLDRRRRDRURUUDDDLLRDRDUDUDUDLLULURULRRLRURUULUULDDDDURULRULLRUDUURLURDUDLUDLUDRLLDUUDUULRLRLUUDRDULDULRURDRRRULRUDLRURDDULUDULLRLRURURUULLULDRURLLRRUUDDUUURRDLURUURULRDRRDDUDULRDDLUDLURURUURDRULLRDDLLRDDLDRDUDRRDLUURRLRLUURRULUDURLDDRLLURRDDDLDDRURULLDDRLUDDLRLURDUDULLRDULLLDLLUDDRUDRUDDUUDRDRULRL
RLRDRDULULUDLUDRDRLUDLDLLUDURULDDDUDLRURLLRLRLDLDRLDURDLRRURLULLULURLLDRRDRLUDRLRDLLULRULURRURURUULRDUDLLRDLRRRRRLUURDRRRDLRUDLLDLLDLRUUUDLLLDDDLRDULLRUUDDRLDDURRRDLRLRLDDDDLRDRULLUURUUDRRLLRLLRDDLLRURRRRDRULRRLLRLLLRLDRRLDDDURRURLDURUURRLRLRLDRURULLRLRUDLDUURDLLRLDLURUUUDLLRDRDDDDDDRLDRRRLRRRRURUDLDDRDLLURUDLRRLDDDLUDUDUULRDULULUDDULUUDLLLLRLDDUUULRLRDULURDURRRURRULURRRDRDLDDURDLURUDURRRDDRLRLUDLUDDLUULLDURLURDDUDDLRUUUDRLLDRURL
ULUDLLUDDULRUURDRURDUDUDLUURDDDRRLUDURURDRURRLDRDURLRLLRRDDRRDRRRUULURUDURUDULRRRRDDLDURRLRRDUDDDRLLLULDRLRLURRDUURDURRRURRDLUDUDDRLDLURRRDDRLLRDRDDRDURRRRLURRLUDDURRULRUDUDULDRUDDRULLUUULDURRRLDRULLURULLRUDLDUDDLDULDLUUDRULULDLLDRULLRUULDUDUUDRLRRLDLUULUDLLDDRLRRDDLLURURDULRRDDRURDRLRLULDLDURULLUUUDURURDLDUDDDDUUULUDLUURRULLDLRLURDLURLRLDDURRLDDRRRDUUULLUULDLLDLLDDRLRRUDLULDRLULDULULRRLRULUUURURUUURDUUDDURLLUDDRLRDDLUURRUULRDLDDRLULUULRDRURLUURDRDUURUDLRR"

# This code assumes the keypad is square
$keypad = @(1, 2, 3), @(4, 5, 6), @(7, 8, 9);
$x = 1;
$y = 1;
$code = ''

foreach ($line in $input.Split()) {
    $line = $line.Trim()
    if ($line) {
        foreach ($command in $line.ToCharArray()) {
            switch ($command) {
                "U" {
                    $y -= 1;
                    break
                }
                "D" {
                    $y += 1;
                    break
                }
                "R" {
                    $x += 1;
                    break
                }
                "L" {
                    $x -= 1;
                    break
                }
                default {
                    Write-Error "Unhandled command type: $command"
                }
            }

            # Check if we tried to move out of the keypad range
            if ($y -le 0) {
                $y = 0;
            } elseif ($y -ge $keypad[0].Count) {
                $y = $keypad[0].Count-1;
            }
            if ($x -le 0) {
                $x = 0;
            } elseif ($x -ge $keypad[0].Count) {
                $x = $keypad[0].Count-1;
            }
        }
        Write-Output "Finding code digit at $x $y, based on $line"
        $digit = $keypad[$y][$x]
        $code += $digit
    }
}

Write-Output "Final code is $code"