2025 Day 1 and Day 2

Author: viandoxdev

2025/.gitignore

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+_build

2025/aoc2025.opam

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+# This file is generated by dune, edit dune-project instead
+opam-version: "2.0"
+synopsis: "AOC 2025 ocaml solutions"
+description: "Advent of Code 2025"
+authors: ["viandoxdev"]
+tags: ["add topics" "to describe" "your" "project"]
+homepage: "https://github.com/viandoxdev/aoc"
+bug-reports: "https://github.com/viandoxdev/aoc/issues"
+depends: [
+  "ocaml"
+  "dune" {>= "3.20"}
+  "odoc" {with-doc}
+]
+build: [
+  ["dune" "subst"] {dev}
+  [
+    "dune"
+    "build"
+    "-p"
+    name
+    "-j"
+    jobs
+    "@install"
+    "@runtest" {with-test}
+    "@doc" {with-doc}
+  ]
+]
+dev-repo: "git+https://github.com/viandoxdev/aoc.git"
+x-maintenance-intent: ["(latest)"]

2025/bin/dune

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+(executable
+ (public_name aoc2025)
+ (name main)
+ (libraries aoc2025 lwt))

2025/bin/main.ml

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+open Aoc2025
+
+let () =
+  let aoc = Aoc.new_ctx () in
+  Aoc.run_days aoc

2025/days/Day01.ml

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+open Utils
+
+let (%%) x y = 
+    let res = x mod y in
+    if res >= 0 then res else res + y
+
+let parse input = 
+    let input = String.sub input 0 (String.length input - 1) in
+    String.split_on_char '\n' input |> List.map (fun s -> 
+        let len = String.length s in
+        let sign = if s.[0] == 'R' then 1 else -1 in
+        let value = int_of_string (String.sub s 1 (len - 1)) in
+        (sign, value)
+    )
+
+let solve_part1 clicks = 
+    List.fold_left (fun (p, a) (sign, value) -> 
+        match ((a + sign * value) mod 100) with
+            | 0 -> (p + 1, 0)
+            | a -> (p, a)) (0, 50) clicks |> fst
+
+let solve_part2 clicks = 
+    List.fold_left (fun (p, a) (sign, value) -> 
+        let na = (a + (value mod 100) * sign) in
+        let np = p + value / 100 + int_of_bool ((a > 0 && na <= 0) || na >= 100) in
+        (np, na %% 100)
+        )
+    (0, 50) clicks |> fst
+
+let day01 input =
+    let clicks = parse input in
+    let part1 = solve_part1 clicks in 
+    let part2 = solve_part2 clicks in 
+  (string_of_int part1, string_of_int part2)

2025/days/Day02.ml

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+open Utils
+
+let parse input =
+    let len = String.length input in
+    String.split_on_char ',' (String.sub input 0 (len - 1))
+        |> List.map (fun s -> (
+            let l = String.length s in
+            let i = String.index_from s 0 '-' in
+            (int_of_string (String.sub s 0 i), int_of_string (String.sub s (i+1) (l - i - 1)))
+        ))
+
+let rec concat_n n x s =
+    if n = 0 then 0
+    else (concat_n (n - 1) x s) * s + x
+
+(* Add all the passwords that are a sequence of d digits repeating rep times in the [a; b] range to list *)
+let invalid_in_range_length_repeat list a b d rep =
+    let shift = p10 d in
+    let limit = p10 (d * rep) in
+    let start = max (a / (p10 (d * rep - d))) (shift / 10) in
+    let rec aux acc x =
+        let r = concat_n rep x shift in
+        if r <= b && r < limit then if r >= a then (
+            aux (r :: acc) (x + 1) 
+        ) else aux acc (x + 1) else acc
+    in
+    aux list start
+(* Add all the passwords that are a sequence of d digits repeated at least twice in the [a; b] range to list *)
+let invalid_in_range_length ?(part1=true) list a b d =
+    let da, db = ilog10 a + 1, ilog10 b + 1 in
+    let rep_min = max ((da + d - 1) / d) 2 in
+    let rep_max = if part1 then 2 else db / d in
+    let rec aux list rep = 
+        if rep > rep_max then list
+        else aux (invalid_in_range_length_repeat list a b d rep) (rep + 1)
+    in
+    aux list rep_min
+
+(* Add all the passwords that are a sequence of digits repeated at least twice in the [a; b] range to list *)
+let invalid_in_range ?(part1=true) (a, b) = 
+    let db = ilog10 b + 1 in
+    let rec aux list d = if d > (db / 2) then list else (
+        aux (invalid_in_range_length ~part1: part1 list a b d) (d+1)) in
+    aux [] 1 |> List.sort_uniq compare |> List.fold_left (+) 0
+
+let solve_part1 = List.fold_left (fun a r -> a + invalid_in_range r) 0
+let solve_part2 = List.fold_left (fun a r -> a + invalid_in_range ~part1: false r) 0
+
+let day02 input =
+    let ranges = parse input in
+    let part1 = solve_part1 ranges in
+    let part2 = solve_part2 ranges in
+    (string_of_int part1, string_of_int part2)
+
+

2025/days/Day03.ml

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+open Utils
+
+let day03 input =
+  ("TODO", "TODO")
+
+

2025/days/Day04.ml

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+open Utils
+
+let day04 input =
+  ("TODO", "TODO")
+
+

2025/days/Day05.ml

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+open Utils
+
+let day05 input =
+  ("TODO", "TODO")
+
+

2025/days/Day06.ml

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+open Utils
+
+let day06 input =
+  ("TODO", "TODO")
+
+