Complete AoC 2015 Day 1

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diff --git a/README.md b/README.md
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+# Advent of Code
+
+This repository contains my solutions to [Advent of Code](https://adventofcode.com/) puzzles. I intend to start from Day 1 of the first year and working through them all. I will probably eventually do this in multiple languages.
+
+All solutions are contained within the `/src` directory and  are named suchly:
+
+`YEAR.DAY.ATTEMPT.EXT`
+
+First attempts (per language) are named `01-first-attempt`, and are never edited afterwards. Editing is why I designed the file naming scheme to handle multiple attempts.
+
+For example:
+- `2015.01.01-first-attempt.c`
+- `2015.01.01-first-attempt.lisp`
+- `2016.05.03-recursive.lisp`
+
+
+## Progress
+
+The following table shows the number of complete attempts I've produced for each problem+language combination.
+
+COMPLETE SOLUTIONS: 0
+
+| DAY     | CL |
+|---------|----|
+| 2015.01 |    |
diff --git a/license.txt b/license.txt
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+++ b/license.txt
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+Copyright © 2024 Tristan Williams
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the “Software”), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
diff --git a/src/2015.01.01-first-attempt.lisp b/src/2015.01.01-first-attempt.lisp
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+;;;; 2015.01.01-first-attempt.lisp
+;;;; Advent of Code 2015 Day 1, first attempt in Lisp
+
+;; ---------------------------------------------------------------------
+;;; Package Definition
+;; ---------------------------------------------------------------------
+
+(defpackage :2015-01-first-attempt
+  (:use #:common-lisp))
+(in-package :2015-01-first-attempt)
+
+
+
+
+;; ---------------------------------------------------------------------
+;;; Definitions
+;; ---------------------------------------------------------------------
+
+(defparameter *PUZZLE-INPUT-FILE* "~/proj/Learn/aoc/src/2015.01._PUZZLE-INPUT.txt"
+  "File to be used as input to the program.")
+
+(defparameter *PUZZLE-INPUT-STRING* (uiop:read-file-string *PUZZLE-INPUT-FILE*)
+  "String version of the text in `*PUZZLE-INPUT-FILE*'.")
+
+(defparameter *PUZZLE-INPUT* (loop for char across *PUZZLE-INPUT-STRING*
+                                   collect char)
+  "Puzzle input in lisp list form.")
+
+
+
+
+;; ---------------------------------------------------------------------
+;;; Part 1
+;; -------
+;; Santa is trying to deliver presents in a large apartment building, but
+;; he can't find the right floor - the directions he got are a little
+;; confusing. He starts on the ground floor (floor 0) and then follows
+;; the instructions one character at a time.
+;;
+;; An opening parenthesis, (, means he should go up one floor, and a
+;; closing parenthesis, ), means he should go down one floor.
+;;
+;; The apartment building is very tall, and the basement is very deep;
+;; he will never find the top or bottom floors.
+;;
+;; For example:
+;;
+;;     (()) and ()() both result in floor 0.
+;;     ((( and (()(()( both result in floor 3.
+;;     ))((((( also results in floor 3.
+;;     ()) and ))( both result in floor -1 (the first basement level).
+;;     ))) and )())()) both result in floor -3.
+;;
+;; To what floor do the instructions take Santa?
+;; ---------------------------------------------------------------------
+
+(defun parse-input (INPUT)
+  "Parse `INPUT' to determine where the instructions take Santa."
+  (let ((FLOOR-NUMBER 0))
+    (+ FLOOR-NUMBER (cond ((eql (first INPUT) nil) 0)
+                          ((eql (first INPUT) #\() (+ 1 (parse-input (rest INPUT))))
+                          ((eql (first INPUT) #\)) (- (parse-input (rest INPUT)) 1))))))
+
+;; Test for correct answer
+(assert (= 138 (parse-input *PUZZLE-INPUT*)))
+
+
+;; I have elected to just throw this away and not do part 2 in this line of thinking.
+;; Keeping it for posterity.
diff --git a/src/2015.01.02-more-lispy-this-time.lisp b/src/2015.01.02-more-lispy-this-time.lisp
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+;;;; 2015.01.02-more-lispy-this-time.lisp
+;;;; Advent of Code 2015 Day 1, first attempt in Lisp
+
+;; ---------------------------------------------------------------------
+;;; Package Definition
+;; ---------------------------------------------------------------------
+
+(defpackage :2015-01-02-more-lispy-this-time
+  (:use #:common-lisp))
+(in-package :2015-01-02-more-lispy-this-time)
+
+
+
+
+;; ---------------------------------------------------------------------
+;;; Definitions
+;; ---------------------------------------------------------------------
+
+(defconstant +PUZZLE-INPUT-FILE+ "~/proj/Learn/aoc/src/2015.01._PUZZLE-INPUT.txt"
+  "File to be used as input to the program.")
+
+(defconstant +PUZZLE-INPUT-STRING+ (uiop:read-file-string +PUZZLE-INPUT-FILE+)
+  "String version of the text in `+PUZZLE-INPUT-FILE+'.")
+
+(defconstant +PUZZLE-INPUT-LIST+ (loop for char across +PUZZLE-INPUT-STRING+
+                                       collect char)
+  "Puzzle input in lisp list form.")
+
+(defconstant +PUZZLE-INPUT-VALUES-LIST+ (mapcar (lambda (INPUT-LIST)
+                                                   (cond ((eql INPUT-LIST #\() 1)
+                                                         ((eql INPUT-LIST #\)) -1)))
+                                                 +PUZZLE-INPUT-LIST+)
+  "Puzzle input converted into floor direction values.")
+
+
+
+
+;; ---------------------------------------------------------------------
+;;; Part 1
+;; -------
+;; Santa is trying to deliver presents in a large apartment building, but
+;; he can't find the right floor - the directions he got are a little
+;; confusing. He starts on the ground floor (floor 0) and then follows
+;; the instructions one character at a time.
+;;
+;; An opening parenthesis, (, means he should go up one floor, and a
+;; closing parenthesis, ), means he should go down one floor.
+;;
+;; The apartment building is very tall, and the basement is very deep;
+;; he will never find the top or bottom floors.
+;;
+;; For example:
+;;
+;;     (()) and ()() both result in floor 0.
+;;     ((( and (()(()( both result in floor 3.
+;;     ))((((( also results in floor 3.
+;;     ()) and ))( both result in floor -1 (the first basement level).
+;;     ))) and )())()) both result in floor -3.
+;;
+;; To what floor do the instructions take Santa?
+;; ---------------------------------------------------------------------
+
+(defun final-floor (INPUT)
+  "Calculate the final floor Santa ends up on given the provided `INPUT'."
+  (apply #'+ INPUT))
+
+(assert (= 138 (final-floor +PUZZLE-INPUT-VALUES-LIST+)))
+
+
+
+
+;; ---------------------------------------------------------------------
+;;; Part 2
+;; -------
+;; Now, given the same instructions, find the position of the first
+;; character that causes him to enter the basement (floor -1). The first
+;; character in the instructions has position 1, the second character
+;; has position 2, and so on.
+;;
+;; For example:
+;;
+;;     ) causes him to enter the basement at character position 1.
+;;     ()()) causes him to enter the basement at character position 5.
+;;
+;; What is the position of the character that causes Santa to first enter the basement?
+;; ---------------------------------------------------------------------
+
+(defun next-floor ()
+  "Determine the result of the next button press, go in that direction, and destroy the information so the Nazis don't get their dirty hands on it."
+  (let ((FLOOR-NUMBER 0)
+        (INPUT-POSITION 0)
+        (INPUT +PUZZLE-INPUT-VALUES-LIST+))
+    (lambda ()
+      (list (incf FLOOR-NUMBER (pop INPUT))
+            (incf INPUT-POSITION)))))
+(defvar next-floor (next-floor))
+
+(defun first-basement-input ()
+  "Determine the position of the input in `+PUZZLE-INPUT-VALUES-LIST' which results in the first entry into the basement (floor -1)."
+  (let ((RESULT (funcall next-floor)))
+    (loop until (= -1 (car RESULT))
+          do (setf RESULT (funcall next-floor)))
+    (cdr RESULT)))
+
+;; Test for correct result
+(assert (= 1771 (first-basement-input)))
diff --git a/src/2015.01._PUZZLE-INPUT.txt b/src/2015.01._PUZZLE-INPUT.txt
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+()(((()))(()()()((((()(((())(()(()((((((()(()(((())))((()(((()))((())(()((()()()()(((())(((((((())))()()(()(()(())(((((()()()((())(((((()()))))()(())(((())(())((((((())())))(()())))()))))()())()())((()()((()()()()(()((((((((()()())((()()(((((()(((())((())(()))()((((()((((((((())()((()())(())((()))())((((()())(((((((((((()()(((((()(()))())(((()(()))())((()(()())())())(()(((())(())())()()(()(()((()))((()))))((((()(((()))))((((()(()(()())())()(((()((((())((((()(((()()(())()()()())((()((((((()((()()))()((()))()(()()((())))(((()(((()))((()((()(()))(((()()(()(()()()))))()()(((()(((())())))))((()(((())()(()(())((()())))((((())))(()(()(()())()((()())))(((()((()(())()()((()((())(()()((())(())()))()))((()(())()))())(((((((()(()()(()(())())))))))(()((((((())((((())((())())(()()))))()(())(()())()())((())(()))))(()))(()((()))()(()((((((()()()()((((((((()(()(())((()()(()()))(())()())()((())))()))()())(((()))(())()(())()))()((()((()(()()())(())()()()((())())))((()()(()()((()(())()()())(((()(()()))))(())))(()(()())()))()()))))))()))))((((((())))())))(()(())())(()())))))(()))()))))))()((()))))()))))(()(()((()())())(()()))))(((())()))())())())(((()(()()))(())()(())(())((((((()()))))((()(()))))))(()))())(((()()(()))()())()()()())))))))))))))(())(()))(()))((()(())(()())(())())(()())(())()()(()())))()()()))(())())()))())())(())((())))))))(())))(())))))()))))((())(()(((()))))(()))()((()(())))(()())(((((()))()())()()))))()))))()))())(()(()()()))()))))))((()))))))))))()((()))((()(())((())()()(()()))()(()))))()()(()))()))(((())))(())()((())(())(()())()())())))))))())))()((())))()))(()))()()))(((((((()))())(()()))(()()(()))()(()((()())()))))))(((()()()())))(())()))()())(()()))()()))))))))(())))()))()()))))))()))()())))()(())(())))))()(())()()(()()))))())((()))))()))))(()(((((()))))))))())))())()(())()()))))(())))())()()())()()())()(()))))()))()))))))))())))((()))()))()))())))()())()()())))())))(()((())()((()))())))))())()(())((())))))))))))())()())(())())())(()))(()))()))())(()(())())()())()()(()))))(()(())))))))(())))())(())))))))())()()(())())())))(())))))()))()(()())()(()))())())))))()()(()))()))))())))))))))()))))()))))))())()())()()))))()())))())))))))))))()()))))()()(((()))()()(())()))))((()))))(()))(())())))(())()))))))(()))()))))(())())))))()))(()())))))))))))))())))))))))()((()())(()())))))))((()))))(())(())))()(()())())))())())(()()()())))()))))))())))))())()()())))))))))))()()(()))))()())()))((()())(()))))()(()))))))))))()())())(((())(()))))())()))()))()))))))()))))))(()))))()))))()(())))(())))(()))())()()(()()))()))(()()))))))))()))(()))())(()()(()(()())()()))()))))))))(())))))((()()(()))())())))))()))())(()())()()))())))()(()()()()))((())())))())()(()()))()))))))))(()))(())))()))))(()(()())(()))))()())())()))()()))())))))))))))())()))))))()))))))))())))))()))))())(()())))(())()))())())))))()()(()()())(()())))()()))(((()))(()()()))))()))))()))))((())))()((((((()()))))))())))))))))))(((()))))))))))))(())())))))())(()))))))(()))((()))())))()(()((()))()))()))))))))))())()))()(()()))))())))())(())()(()))()))())(()))()))))(()()))()()(())))))()))(())(()(()()))(()()())))))(((()))))))()))))))))))))(())(()))))()())())()()((()()))())))))(()))))())))))))()()()))))))))())))()(((()()))(())))))(((())())))))((()))()(()))(()))))(()())))(()))())))))()))))(())(())))()((()))(())())))()()))()))))))))()))(()()()(()()()(()))())(())()())(((()))(())))))))))(((()())))()()))))))))()(())(()))()((((())(())(()())))()))(((())()()()))((()))(()))())())))())))(()))())()())())(()(())())()()()(())))())(())))(())))(())()))()))(()((()))))))))())(()))))))())(()()))()()))()(()(()())))()()(()((()((((((()))(())))()()()))())()))((()()(()))())((()(()(()))(()()))))()())))()))()())))))))()()((()())(())))()))(()))(())(()))())(()(())))()()))))))(((()(((()()))()(()(())())((()()))()))()))()))()(()()()(()))((()())()(())))()()))(((())()()())(())()((()()()()(()(())(()()))()(((((()())))((())))))(()()()))))(((()(())))()))((()((()(())()(()((())))((()())()(()))(((()())()()(()))(())(((()((()())()((())()())(((()()))((()((())(()))(()())(()()()))((()))(())(()((()()())((()))(())))(())(())(())))(()())))(((((()(()(((((()())((((()(()())(())(()()(((())((()(((()()(((()()((((((())))())(()((((((()(()))()))()()((()((()))))()(()()(()((()()))))))(((((()(((((())()()()(())())))))))()))((()()(())))(())(()()()())))))(()((((())))))))()()(((()(()(()(()(()())()()()(((((((((()()())()(()))((()()()()()(((((((()())()((())()))((((((()(()(()(()())(((()(((((((()(((())(((((((((())(())())()))((()(()))(((()()())(())(()(()()(((()(())()))())))(())((((((())(()()())()()(((()(((())(()(((())(((((((()(((((((((()))(())(()(()(()))))((()))()(())())())((()(()((()()))((()()((()(())(())(()((())(((())(((()()()((((((()()(())((((())()))))(())((()(()((())))(((((()(()()())())((())())))((())((()((()()((((((())(((()()(()())())(()(()))(()(()))())())()(((((((()(((()(())()()((())((()(()()((()(()()(((((((((((())((())((((((())((()((((()(()((((()(((((((())()((()))))())()((()((((()(()(((()((()())))(())())(((()(((())((((((()(((((((((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