first 4 days

3/main.ml

@@ -0,0 +1,47 @@
+open Printf;;
+open String;;
+open Str;;
+
+let read_whole_file f =
+  let s = really_input_string f (in_channel_length f) in
+  close_in f;
+  s
+
+let rec process_all_mul_inner re str pos acc =
+  try
+    let new_pos = Str.search_forward re str pos in
+    let n1 = int_of_string @@ Str.matched_group 1 str in
+    let n2 = int_of_string @@ Str.matched_group 2 str in
+    process_all_mul_inner re str (new_pos + 1) (acc + n1 * n2)
+  with Not_found -> acc
+let rec process_all_mul_with_dont_inner re str enabled pos acc =
+  try
+    let new_pos = Str.search_forward re str pos in
+    let command = Str.matched_group 0 str in
+    if command = "do()" then
+      process_all_mul_with_dont_inner re str true (new_pos + 1) acc
+    else if command = "don't()" then
+      process_all_mul_with_dont_inner re str false (new_pos + 1) acc
+    else if enabled then
+      let n1 = int_of_string @@ Str.matched_group 1 str in
+      let n2 = int_of_string @@ Str.matched_group 2 str in
+      process_all_mul_with_dont_inner re str enabled (new_pos + 1) (acc + n1 * n2)
+    else
+      process_all_mul_with_dont_inner re str enabled (new_pos + 1) acc
+  with Not_found -> acc
+
+let process_all_mul str =
+  let re = Str.regexp "mul(\\([0-9]+\\),\\([0-9]+\\))" in
+  process_all_mul_inner re str 0 0
+
+let process_all_mul_with_dont str =
+  let re = Str.regexp "mul(\\([0-9]+\\),\\([0-9]+\\))\\|do()\\|don't()" in
+  process_all_mul_with_dont_inner re str true 0 0
+
+let () =
+  let f = open_in "input.txt" in
+  let str = read_whole_file f in
+  let result = process_all_mul str in
+  let result2 = process_all_mul_with_dont str in
+  printf "%d\n" result;
+  printf "%d\n" result2