Advent of Code 2023 Day 01

main.adb

with Text_IO; use Text_IO;
with Ada.Integer_Text_IO; use Ada.Integer_Text_IO;
with Ada.Strings.Unbounded;
with Ada.Characters.Handling;

procedure main is
	package SU renames Ada.Strings.Unbounded;
	package CH renames Ada.Characters.Handling;
	InputFile : File_Type;
	Fname : constant String := "input.txt";
	CurrentLine : SU.Unbounded_String;
	CurrentChoppedLine : SU.Unbounded_String;
	FirstDigit : Integer;
	LastDigit : Integer;
	Accum : Integer := 0;
	CurrentChar : Character;
	AsciiDigitBase : Integer := Character'Pos('0');
	CurrentCharAsInt : Integer;
	FirstDigitSeen : Boolean;
	FoundDigit : Boolean;

	-- Check whether <Text> begins with <SearchWord>
	function Find(Text : in String; SearchWord : in String) return Boolean is
	begin
		if SearchWord'Length > Text'Length then
			return False;
		end if;

		for I in 1..SearchWord'Length loop
			if SearchWord(I) /= Text(I) then
				return False;
			end if;
		end loop;

		return True;
	end Find;

	-- Try to find a written out digit at the beginning of <Str>, and if found,
	-- write its integer value to <Value>. Returns whether a digit was found.
	function LookForWrittenDigit(Str : in String; Value : out Integer) return Boolean is
	begin
		if Find(Str, "one") then
			Value := 1;
			return True;
		elsif Find(Str, "two") then
			Value := 2;
			return True;
		elsif Find(Str, "three") then
			Value := 3;
			return True;
		elsif Find(Str, "four") then
			Value := 4;
			return True;
		elsif Find(Str, "five") then
			Value := 5;
			return True;
		elsif Find(Str, "six") then
			Value := 6;
			return True;
		elsif Find(Str, "seven") then
			Value := 7;
			return True;
		elsif Find(Str, "eight") then
			Value := 8;
			return True;
		elsif Find(Str, "nine") then
			Value := 9;
			return True;
		end if;

		return False;
	end LookForWrittenDigit;
begin
	Open(InputFile, In_File, Fname);

	while not End_Of_File(InputFile) loop
		CurrentLine := SU.To_Unbounded_String(Get_Line(InputFile));

		FirstDigit := 0;
		LastDigit := 0;
		FirstDigitSeen := False;
		CurrentChoppedLine := CurrentLine;
		FoundDigit := False;

		for I in 1..SU.Length(CurrentLine) loop
			CurrentChar := SU.Element(CurrentChoppedLine, 1);

			-- Check char digit first
			if CH.Is_Digit(CurrentChar) then
				CurrentCharAsInt := Character'Pos(CurrentChar) - AsciiDigitBase;
				FoundDigit := True;
			-- Then check written out digit
			elsif LookForWrittenDigit(SU.To_String(CurrentChoppedLine), CurrentCharAsInt) then
				FoundDigit := True;
			end if;

			if FoundDigit then
				LastDigit := CurrentCharAsInt;
				if not FirstDigitSeen then
					FirstDigitSeen := True;
					FirstDigit := CurrentCharAsInt;
				end if;
				FoundDigit := False;
			end if;

			-- Continuously chop off the first character of the line
			CurrentChoppedLine :=
				SU.Unbounded_Slice(CurrentChoppedLine, 2, SU.Length(CurrentChoppedLine));

		end loop;

		-- First and LastDigit now have the correct values for the current line
		Accum := Accum + (FirstDigit * 10) + LastDigit;
	end loop;

	Put("Accum: ");
	Put_Line(Integer'Image(Accum));

	Close(InputFile);
end main;