2018-05a

DEFLNG A-Z
DIM b(50000) AS _BYTE, s(50000) AS _BYTE

OPEN "input05.txt" FOR BINARY AS #1
GET #1, , b()
CLOSE #1

FOR i = 0 TO 49999
  IF ABS(s(p) - b(i)) <> 32 THEN p = p + 1: s(p) = b(i) ELSE p = p - 1
NEXT
PRINT "Part 1:"; p

b() = s()
FOR c = 1 TO 26: p = 0
  FOR i = 0 TO 49999
    IF b(i) <> c + 64 AND b(i) <> c + 96 THEN
      IF ABS(s(p) - b(i)) <> 32 THEN p = p + 1: s(p) = b(i) ELSE p = p - 1
    END IF
  NEXT
  PRINT CHR$(c + 64); p; " | ";
NEXT