(ql:quickload "str")

(defparameter *input-file* #P"input.txt")
(defparameter *input* (uiop:read-file-string *input-file*))

(defun execute (program)
  (loop for i from 0 by 4 until (= 99 (aref program i))
     do (let ((opcode (aref program i)))
	  (cond ((= opcode 1)
		 (setf (aref program (aref program (+ 3 i)))
		       (+ (aref program (aref program (+ 1 i)))
			  (aref program (aref program (+ 2 i))))))
		((= opcode 2)
		 (setf (aref program (aref program (+ 3 i)))
		       (* (aref program (aref program (+ 1 i)))
			  (aref program (aref program (+ 2 i)))))))))
  program)

(defun execute-with-inputs (program-string noun verb)
    (let ((program (map 'vector #'parse-integer (str:split "," program-string))))
      (setf (aref program 1) noun)
      (setf (aref program 2) verb)
      (aref (execute program) 0)))

(defun part1 (program-string)
  (execute-with-inputs program-string 12 2))

(defun part2 (program-string)
  (dotimes (noun 99)
    (dotimes (verb 99)
      (when (= 19690720 (execute-with-inputs program-string noun verb))
	(return-from part2 (+ (* 100 noun) verb))))))