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AdventOfCode2023
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Added some improvements for TBigInt shift left operator

This commit is contained in:
Stefan Müller 2024-05-23 22:01:25 +02:00
parent 4329041353
commit 2df8266d42
2 changed files with 42 additions and 39 deletions
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78
UBigInt.pas
View File

@ -626,49 +626,51 @@ var
begin
// Handles shift of zero.
if A = 0 then
Result := TBigInt.Zero
else begin
// Determines full digit shifts and bit shifts.
DivMod(B, CBitsPerDigit, digitShifts, bitShifts);
begin
Result := TBigInt.Zero;
Exit;
end;
if bitShifts > 0 then
// Determines full digit shifts and bit shifts.
DivMod(B, CBitsPerDigit, digitShifts, bitShifts);
if bitShifts > 0 then
begin
reverseShift := CBitsPerDigit - bitShifts;
len := Length(A.FDigits);
lastDigit := A.FDigits[len - 1] >> reverseShift;
newLength := len + digitShifts;
if lastDigit = 0 then
SetLength(Result.FDigits, newLength)
else
SetLength(Result.FDigits, newLength + 1);
// Performs full digit shifts by shifting the access index j for A.FDigits.
Result.FDigits[digitShifts] := A.FDigits[0] << bitShifts;
j := 0;
for i := digitShifts + 1 to newLength - 1 do
begin
reverseShift := CBitsPerDigit - bitShifts;
len := Length(A.FDigits);
lastDigit := A.FDigits[len - 1] >> reverseShift;
newLength := len + digitShifts;
if lastDigit = 0 then
SetLength(Result.FDigits, newLength)
else
SetLength(Result.FDigits, newLength + 1);
// Performs full digit shifts by shifting the access index j for A.FDigits.
Result.FDigits[digitShifts] := A.FDigits[0] << bitShifts;
j := 0;
for i := digitShifts + 1 to newLength - 1 do
begin
// Performs bit shifts.
Result.FDigits[i] := A.FDigits[j] >> reverseShift;
Inc(j);
Result.FDigits[i] := Result.FDigits[i] or (A.FDigits[j] << bitShifts);
end;
if Length(Result.FDigits) > newLength then
Result.FDigits[newLength] := lastDigit;
end
else begin
// Performs full digit shifts by copy if there are no bit shifts.
len := Length(A.FDigits);
SetLength(Result.FDigits, len + digitShifts);
for i := 0 to digitShifts - 1 do
Result.FDigits[i] := 0;
for i := 0 to len - 1 do
Result.FDigits[i + digitShifts] := A.FDigits[i];
// Performs bit shifts.
Result.FDigits[i] := A.FDigits[j] >> reverseShift;
Inc(j);
Result.FDigits[i] := Result.FDigits[i] or (A.FDigits[j] << bitShifts);
end;
Result.FIsNegative := A.IsNegative;
if lastDigit > 0 then
Result.FDigits[newLength] := lastDigit;
end
else begin
// Performs full digit shifts by copy if there are no bit shifts.
len := Length(A.FDigits);
SetLength(Result.FDigits, len + digitShifts);
for i := 0 to digitShifts - 1 do
Result.FDigits[i] := 0;
for i := 0 to len - 1 do
Result.FDigits[i + digitShifts] := A.FDigits[i];
end;
Result.FIsNegative := A.IsNegative;
end;
operator shr(const A: TBigInt; const B: Integer): TBigInt;

3
tests/UBigIntTestCases.pas
View File

@ -732,7 +732,8 @@ end;
{ TBigIntShiftLeftTestCase }
procedure TBigIntShiftLeftTestCase.Test(const AHexValueOperand: string; const AShift: Integer; const AHexValueResult: string);
procedure TBigIntShiftLeftTestCase.Test(const AHexValueOperand: string; const AShift: Integer; const AHexValueResult:
string);
var
a, s: TBigInt;
begin