AdventOfCode2023/solvers/UWaitForIt.pas

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{
Solutions to the Advent Of Code.
Copyright (C) 2023 Stefan Müller
This program is free software: you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free Software
Foundation, either version 3 of the License, or (at your option) any later
version.
This program is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with
this program. If not, see <http://www.gnu.org/licenses/>.
}
unit UWaitForIt;
{$mode ObjFPC}{$H+}
interface
uses
Classes, SysUtils, Generics.Collections, Math, USolver;
type
{ TWaitForIt }
TWaitForIt = class(TSolver)
private
FTimes, FDistances: specialize TList<Cardinal>;
FLongTime, FLongDistance: UInt64;
function CalcRange(const ATime, ADistance: UInt64): Cardinal;
public
constructor Create;
destructor Destroy; override;
procedure ProcessDataLine(const ALine: string); override;
procedure Finish; override;
function GetDataFileName: string; override;
function GetPuzzleName: string; override;
end;
implementation
{ TWaitForIt }
function TWaitForIt.CalcRange(const ATime, ADistance: UInt64): Cardinal;
var
x1, x2: Integer;
p, s: Double;
begin
p := ATime / 2;
s := Sqrt(p * p - ADistance);
x1 := Math.Floor(p - s + 1);
x2 := Math.Ceil(p + s - 1);
Result := x2 - x1 + 1;
end;
constructor TWaitForIt.Create;
begin
FTimes := specialize TList<Cardinal>.Create;
FDistances := specialize TList<Cardinal>.Create;
end;
destructor TWaitForIt.Destroy;
begin
FTimes.Free;
FDistances.Free;
inherited Destroy;
end;
procedure TWaitForIt.ProcessDataLine(const ALine: string);
var
split: TStringArray;
list: specialize TList<Cardinal>;
value: PUInt64;
i: Integer;
cleaned: string;
begin
split := ALine.Split([' ', ':']);
if split[0] = 'Time' then
begin
list := FTimes;
value := @FLongTime;
end
else if split[0] = 'Distance' then
begin
list := FDistances;
value := @FLongDistance;
end
else
Exit;
cleaned := '';
for i := 1 to Length(split) - 1 do
if split[i] <> '' then
begin
list.Add(StrToDWord(split[i]));
cleaned := Concat(cleaned, split[i]);
end;
value^ := StrToUInt64(cleaned);
end;
procedure TWaitForIt.Finish;
var
i: Integer;
begin
FPart1 := 1;
for i := 0 to FTimes.Count - 1 do
FPart1 := FPart1 * CalcRange(FTimes[i], FDistances[i]);
FPart2 := CalcRange(FLongTime, FLongDistance);
end;
function TWaitForIt.GetDataFileName: string;
begin
Result := 'wait_for_it.txt';
end;
function TWaitForIt.GetPuzzleName: string;
begin
Result := 'Day 6: Wait For It';
end;
end.