Optimise solutions a bit for 2024

2015/README.txt

@@ -18,12 +18,12 @@ I want to do this advent of code in more than one language if possible.
 Here is a list of all the languages I am aware of enough to program in,
 ordered from least to most confidence:
 
-- (0) POSIX Shell
+- (1) POSIX Shell
-- (0) Haskell
+- (2) Haskell
-- (0) Ocaml
+- (3) Ocaml
-- (0) Rust
+- (4) Racket
-- (0) Racket
+- (5) Rust
-- (0) JavaScript/TypeScript
+- (6) JavaScript/TypeScript
 - (0) Common Lisp
 - (0) C
 - (0) Python

2015/puzzle-4.rkt

@@ -0,0 +1,20 @@
+#lang racket
+
+(require racket/file)
+(require file/md5)
+
+(define input (file->string "4-input"))
+
+(define (find-salt requested-string current)
+  (let* ([full-message (string-append input (number->string current))]
+         [hash (bytes->string/locale (md5 full-message))])
+    (if (string-prefix? hash requested-string)
+        current
+        (find-salt requested-string (+ current 1)))))
+
+(printf "Round 1: ~a~%" (find-salt "00000"  0))
+(printf "Round 2: ~a~%" (find-salt "000000" 0))
+
+;; Local Variables:
+;; compile-command: "racket puzzle-4.rkt"
+;; End:

2015/puzzle-5.rs

@@ -0,0 +1,80 @@
+use std::fs;
+
+const VOWELS_STR: &str = "aeiou";
+const DO_NOT_WANT: [&str; 4] = ["ab", "cd", "pq", "xy"];
+
+fn is_nice_round1(line: &str) -> bool {
+    let mut unwanted_substr = false;
+    let mut has_consecutive = false;
+    let mut vowels = 0;
+    for i in 0..line.len() - 1 {
+        let slide: &str = &line[i..i + 2];
+        if DO_NOT_WANT.iter().position(|&x| x == slide).is_some() {
+            unwanted_substr = true;
+            break;
+        }
+        let first = slide.chars().nth(0).unwrap();
+        let second = slide.chars().nth(1).unwrap();
+        if VOWELS_STR.contains(first) {
+            vowels += 1;
+        }
+        if first == second {
+            has_consecutive = true;
+        }
+    }
+
+    if VOWELS_STR.contains(line.chars().nth(line.len() - 1).unwrap()) {
+        vowels += 1;
+    }
+
+    if unwanted_substr {
+        return false;
+    }
+    return vowels >= 3 && has_consecutive;
+}
+
+fn is_nice_round2(line: &str) -> bool {
+    /*
+    Justifying the O(|line|^2) runtime is easy: |line| is constant, such that at
+    worst we're doing roughly O(256) iterations.  Not too bad.
+
+    If |line| could be really big I'd look into optimising the rest, but why do
+    that?
+     */
+    let mut has_pair = false;
+
+    // Unfortunate O(|line|^2) runtime
+    for i in 0..line.len() - 1 {
+        let slide = &line[i..i + 2];
+        let rest = &line[i + 2..];
+        if rest.contains(slide) {
+            has_pair = true;
+            break;
+        }
+    }
+
+    // O(|line|) runtime
+    let mut has_triple = false;
+    for i in 0..line.len() - 2 {
+        let slide = &line[i..i + 3];
+        if slide.chars().nth(0) == slide.chars().nth(2) {
+            has_triple = true;
+            break;
+        }
+    }
+
+    return has_pair && has_triple;
+}
+
+fn main() {
+    let binding = fs::read_to_string("5-input").expect("wget 5-input please.");
+    let contents: Vec<&str> = binding.split("\n").collect();
+    let nice_lines_1 = contents.iter().filter(|&x| is_nice_round1(x)).count();
+    let nice_lines_2 = contents.iter().filter(|&x| is_nice_round2(x)).count();
+    println!("Round 1: {nice_lines_1}");
+    println!("Round 2: {nice_lines_2}");
+}
+
+// Local Variables:
+// compile-command: "rustc puzzle-5.rs && ./puzzle-5"
+// End:

2015/puzzle-6.js

@@ -0,0 +1,83 @@
+const fs = require('node:fs/promises');
+
+let arr = []
+
+function count_1() {
+  return arr.filter(x => x).length;
+}
+
+function count_2() {
+  return arr.reduce((x, y) => x + y);
+}
+
+async function read_file() {
+  const data = await fs.readFile("6-input", {encoding: 'utf8'});
+  return data;
+}
+
+function parse_line(line) {
+  let [type, ...rest] = line.split(" ")
+  let obj = {type: "", bottom: [], top: []};
+  if (type === "toggle") {
+    obj.type = "toggle";
+  } else {
+    obj.type = rest[0];
+    rest = rest.slice(1);
+  }
+  obj.bottom = rest[0].split(",").map(x => parseInt(x));
+  obj.top = rest[2].split(",").map(x => parseInt(x));
+  return obj
+}
+
+function execute_inst_1(inst) {
+  for (let i = inst.bottom[0]; i <= inst.top[0]; ++i) {
+    for (let j = inst.bottom[1]; j <= inst.top[1]; ++j) {
+      if (inst.type === "on") {
+        arr[(i * 1000) + j] = true;
+      } else if (inst.type === "off") {
+        arr[(i * 1000) + j] = false;
+      } else {
+        arr[(i * 1000) + j] = !arr[(i * 1000) + j];
+      }
+    }
+  }
+}
+
+function execute_inst_2(inst) {
+  for (let i = inst.bottom[0]; i <= inst.top[0]; ++i) {
+    for (let j = inst.bottom[1]; j <= inst.top[1]; ++j) {
+      if (inst.type === "on") {
+        arr[(i * 1000) + j] += 1;
+      } else if (inst.type === "off") {
+        arr[(i * 1000) + j] = Math.max(0, arr[(i * 1000) + j] - 1);
+      } else {
+        arr[(i * 1000) + j] += 2;
+      }
+    }
+  }
+}
+
+(async () => {
+  let lines = (await read_file()).split(/\n/);
+  const insts = lines.map(parse_line);
+
+  for (let i = 0; i < 1000000; ++i) {
+    arr.push(false);
+  }
+  for (let i = 0; i < insts.length; ++i) {
+    execute_inst_1(insts[i]);
+  }
+  console.log("Round 1:", count_1());
+
+  for (let i = 0; i < 1000000; ++i) {
+    arr[i] = 0;
+  }
+  for (let i = 0; i < insts.length; ++i) {
+    execute_inst_2(insts[i]);
+  }
+  console.log("Round 2:", count_2());
+})()
+
+// Local Variables:
+// compile-command: "node puzzle-6.js"
+// End:

2024/puzzle-1.lisp

@@ -0,0 +1,15 @@
+(load "util.lisp")
+
+(--> (uiop:read-file-lines "1-input")
+     (loop for line in _
+           for x = (search "   " line)
+           collect (parse-integer (subseq line 0 x)) into left
+           collect (parse-integer (subseq line (+ x 3))) into right
+           finally (return (list (sort left #'<) (sort right #'<))))
+     (format t "Round 1: ~a~%Round 2: ~a~%"
+             (loop for x in (car _)
+                   for y in (cadr _)
+                   sum (abs (- y x)))
+             (loop for item in (car _)
+                   for count = (count item (cadr _))
+                   sum (* item count))))

2024/puzzle-2.py

@@ -0,0 +1,43 @@
+lines = []
+with open("2-input", "r") as fp:
+    lines = fp.readlines()
+
+levels = [list(map(int, line.strip().split(" "))) for line in lines]
+
+def is_good_level_1(level):
+    # 1) Is decreasing
+    # 2) Sliding window of two cells (x, y) => 1 <= |x-y| <= 3
+    # figure out if decreasing from first two
+    decreasing = level[0] > level[1]
+    for i in range(len(level) - 1):
+        x = level[i]
+        y = level[i + 1]
+        diff = abs(x - y)
+        if (decreasing and x < y) or (not decreasing and x > y) or not (diff <= 3 and diff >= 1):
+            return False
+    return True
+
+good_levels = [level for level in levels if is_good_level_1(level)]
+print(f"Round 1: {len(good_levels)}")
+
+def check_two_levels(x, y, decreasing):
+    diff = abs(x - y)
+    return not ((decreasing and x < y)\
+           or (not decreasing and x > y) \
+           or not (diff <= 3 and diff >= 1))
+
+def is_good_level_2(level):
+    # 1) Is decreasing
+    # 2) Sliding window of two cells (x, y) => 1 <= |x-y| <= 3
+    # 3) Can remove any one item to make it safe
+    if is_good_level_1(level):
+        return True
+    # Consider slices of the level and check if they're good
+    slices = [level[:i] + level[i + 1:] for i in range(len(level))]
+    for s in slices:
+        if is_good_level_1(s):
+            return True
+    return False
+
+good_levels = [level for level in levels if is_good_level_2(level)]
+print(f"Round 2: {len(good_levels)}")

2024/puzzle-3.lisp

@@ -0,0 +1,59 @@
+(load "util.lisp")
+
+(defparameter input (uiop:read-file-string "3-input"))
+
+(defun is-good-mul (str)
+  (let ((start (search "(" str))
+        (middle (search "," str))
+        (end (search ")" str)))
+    (and (not (null start)) (not (null middle)) (not (null end))
+         ;; mul( <- 3 character
+         (eq start 3)
+         ;; Simple to understand
+         (< start end)
+         (< start middle)
+         (< middle end)
+         ;; Make sure the arguments are purely numbers
+         (every #'digit-char-p (subseq str (1+ start) middle))
+         (every #'digit-char-p (subseq str (1+ middle) end)))))
+
+(defun parse-mul (str)
+  (let ((start (search "(" str))
+        (middle (search "," str))
+        (end (search ")" str)))
+    (list (parse-integer (subseq str (1+ start) middle))
+          (parse-integer (subseq str (1+ middle) end)))))
+
+(defun parse-input-muls (line)
+  (let ((possible (search-all "mul" line)))
+    (--> (cdr possible)
+         (append _ (list (length line)))
+         ;; index of mul -> (position substring)
+         (mapcar (lambda (z1 z2) (cons z1 (subseq line z1 z2))) possible _)
+         ;; remove any bad muls
+         (remove-if-not (lambda (x) (is-good-mul (cdr x))) _)
+         ;; parse muls
+         (mapcar (lambda (x) (cons (car x) (parse-mul (cdr x)))) _))))
+
+(format t "Round 1: ~a~%"
+        (loop for (pos x y) in (parse-input-muls input)
+              sum (* x y)))
+
+(defun parse-input-conds (input)
+  (let ((dos (search-all "do()" input))
+        (donts (search-all "don't()" input)))
+    (--> (append (mapcar (lambda (x) (cons 'do x)) dos)
+                 (mapcar (lambda (x) (cons 'dont x)) donts))
+         (sort _ (lambda (x y) (< (cdr x) (cdr y))))
+         (cons '(do . 0) _))))
+
+(defun current-cond (pos conds)
+  (caar (last (remove-if (lambda (x) (> (cdr x) pos)) conds))))
+
+(format t "Round 2: ~a~%"
+        (let ((conds (parse-input-conds input))
+              (muls (parse-input-muls input)))
+          (loop for (pos x y) in muls
+                for current = (current-cond pos conds)
+                if (eq current 'do)
+                  sum (* x y))))

2024/util.lisp

@@ -0,0 +1,20 @@
+(defmacro --> (first &rest functions)
+  (if (null functions)
+      first
+      `(let* ,(loop :for f :in (cons first functions)
+                    :appending `((_ ,f)))
+         _)))
+
+(defun search-all (substr str &optional acc len)
+  (let ((x (search substr str))
+        (len (or len 0)))
+    (if (null x)
+        (reverse acc)
+        (search-all substr (subseq str (1+ x))
+                    (cons (+ x len) acc)
+                    (+ len x 1)))))
+
+  (defun zip (a b)
+    (loop for i in a
+          for j in b
+          collect (cons i j)))