From 3b7bfa3103df55a42a9164465c4b750d0f1f36a0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Stefan=20M=C3=BCller?= <stefan.mueller@aksdb.de>
Date: Sat, 2 Dec 2023 17:50:06 +0100
Subject: [PATCH] Updated the solution for day 1, part 1 to facilitate part 2

---
 puzzles/utrebuchet.pas | 69 ++++++++++++++++++++++++++++++------------
 1 file changed, 49 insertions(+), 20 deletions(-)

diff --git a/puzzles/utrebuchet.pas b/puzzles/utrebuchet.pas
index 7bbbaeb..7abb7b5 100644
--- a/puzzles/utrebuchet.pas
+++ b/puzzles/utrebuchet.pas
@@ -33,9 +33,12 @@ type
     FValue: Integer;
     procedure RunSolution;
     procedure ProcessDataLine(const ALine: string);
+    function FindFirstDigit(const ALine: string; out OEndIndex: Integer): Integer;
+    function FindLastDigit(const ALine: string; const AFirstDigit, AFirstDigitEndIndex: Integer): Integer;
+    function CheckDigit(const ALine: string; const AIndex: Integer; out ODigit, OEndIndex: Integer): Boolean;
   public
-    class procedure Solve; static;
     constructor Create;
+    class procedure Solve; static;
   end;
 
 implementation
@@ -58,28 +61,59 @@ begin
   finally
     CloseFile(data)
   end;
-  WriteLn(FValue);
+  WriteLn('Part 1: ', FValue);
 end;
 
 procedure TTrebuchet.ProcessDataLine(const ALine: string);
 var
-  c: Char;
-  first, last: Integer;
+  first, endIndex, last: Integer;
 begin
-  first := -1;
-  last := -1;
-  for c in ALine do
-  begin
-    if c in ['0'..'9'] then
-    begin
-      last := StrToInt(c);
-      if first < 0 then
-        first := last;
-    end;
-  end;
+  first := FindFirstDigit(ALine, endIndex);
+  last := FindLastDigit(ALine, first, endIndex);
   Inc(FValue, first * 10 + last);
 end;
 
+function TTrebuchet.FindFirstDigit(const ALine: string; out OEndIndex: Integer): Integer;
+var
+  i: Integer;
+begin
+  for i := 1 to ALine.Length do
+    if CheckDigit(ALine, i, Result, OEndIndex) then
+      Exit;
+end;
+
+function TTrebuchet.FindLastDigit(const ALine: string; const AFirstDigit, AFirstDigitEndIndex: Integer): Integer;
+var
+  i, endIndex: Integer;
+begin
+  for i := ALine.Length downto AFirstDigitEndIndex + 1 do
+    if CheckDigit(ALine, i, Result, endIndex) then
+      Exit;
+
+  // Returns the first digit if no digit was found after the end index of the first digit.
+  Result := AFirstDigit;
+end;
+
+function TTrebuchet.CheckDigit(const ALine: string; const AIndex: Integer; out ODigit, OEndIndex: Integer): Boolean;
+begin
+  if ALine[AIndex] in ['0'..'9'] then
+  begin
+    ODigit := StrToInt(ALine[AIndex]);
+    OEndIndex := AIndex;
+    Result := true;
+  end
+  else begin
+    ODigit := -1;
+    OEndIndex := -1;
+    Result := false;
+  end;
+end;
+
+constructor TTrebuchet.Create;
+begin
+  FValue := 0;
+end;
+
 class procedure TTrebuchet.Solve;
 var
   trebuchet: TTrebuchet;
@@ -90,10 +124,5 @@ begin
   trebuchet.Free;
 end;
 
-constructor TTrebuchet.Create;
-begin
-  FValue := 0;
-end;
-
 end.