Solution day 7 part 1

7/dune

@@ -0,0 +1,3 @@
+(executables
+ (names  solve_1 solve_2)
+ (libraries base stdio str))

7/solve_1.ml

@@ -0,0 +1,44 @@
+open Stdio
+open Str
+
+type equation = {
+  result: int;
+  operands: int list;
+}
+
+let input_info = 
+  let rec aux equation_list = 
+    let line = In_channel.input_line In_channel.stdin in
+    (match line with
+    | None -> equation_list
+    | Some x -> 
+      let parts = split (regexp ":") x in
+      match parts with
+      | result :: operands -> 
+        let result_int = int_of_string result in
+        let operands = split (regexp " ") (List.hd operands) in
+        let operands_int = List.map int_of_string operands in
+        aux ({result = result_int; operands = operands_int} :: equation_list)
+      | [] -> aux equation_list)
+  in aux []
+;;
+
+
+let is_equation_true equ =
+  let nb_operators = (List.length equ.operands) - 1 in
+  let rec aux idx accum l = 
+    if idx == nb_operators then ((accum == equ.result), equ.result) else
+    match l with
+    | [] -> (false,equ.result)
+    | hd :: tl -> (fst ((aux (idx+1) (accum + hd) tl)) ||
+                   fst ((aux (idx+1) (accum * hd) tl)), equ.result) in
+  aux 0 (List.hd equ.operands) (List.tl equ.operands)
+;;
+
+let solve = 
+  let are_equations_true = List.map is_equation_true input_info in
+  let results = List.map (fun x -> if (fst x) then (snd x) else 0) are_equations_true in
+  List.fold_left (+) 0 results;
+;;
+
+let () = printf "Total: %d\n" solve;;

README.md

@@ -47,8 +47,8 @@ replace `<part_number>` with 1 for Part 1 or 2 for Part 2
 | 3   | ✅     | ✅     |
 | 4   | ✅     | ✅     |
 | 5   | ✅     | ✅     |
-| 6   | ✅     | ⬜     |
-| 7   | ⬜     | ⬜     |
+| 6   | ✅     | ✅     |
+| 7   | ✅     | ⬜     |
 | 8   | ⬜     | ⬜     |
 | ... | ...    | ...    |
 | 25  | ⬜     | ⬜     |