The problem here looks like its a stack overflow from too much recursion (5000 recursive calls looks like about the right number of calls to blow out a Java call stack) and not a limitation of BigInteger. Rewriting the factorial function iteratively should fix this. For example: public static BigInteger factorial(BigInteger n) { BigInteger result … Read more
You actually should ensure that you type what you mean: $bigint = 9999999999999999999; Is not a PHP integer but float: float(1.0E+19) If you would have done $bigint = (int) 9999999999999999999; You would have set an integer in fact, but it would not be the number you might have expected: int(-8446744073709551616) It’s no problem at all … Read more
You can use System.Numerics.BigInteger (add a reference to System.Numerics assembly). As mentioned in the comments this might not be the right approach though.
The remarks for the BigInteger constructor state that you can make sure any BigInteger created from a byte[] is unsigned if you append a 00 byte to the end of the array before calling the constructor. Note: the BigInteger constructor expects the array to be in little-endian order. Keep that in mind if you expect … Read more
Check if BigInteger is not a perfect square has code to compute the integer square root of a Java BigInteger. Here it is translated into C#, as an extension method. public static BigInteger Sqrt(this BigInteger n) { if (n == 0) return 0; if (n > 0) { int bitLength = Convert.ToInt32(Math.Ceiling(BigInteger.Log(n, 2))); BigInteger root … Read more
Hopefully helpfull links : http://php.net/manual/en/ref.bc.php http://php.net/manual/en/ref.gmp.php EDIT: Math_BigInteger Example from http://phpseclib.sourceforge.net/documentation/math.html : Implements an arbitrary precision integer arithmetic library. Uses gmp or bcmath, if available, and an internal implementation, otherwise. <?php include(‘Math/BigInteger.php’); $a = new Math_BigInteger(2); $b = new Math_BigInteger(3); $c = $a->add($b); echo $c->toString(); // outputs 5 ?>
If you can’t use a big-integer library, and you don’t have a native uint128_t (or similar), you’ll need to do this manually. One option is to express a as the sum of two 32-bit quantities, i.e. a = 232b + c, where b contains the 32 msbs, and c contains the 32 lsbs. Squaring is … Read more
Here’s a fast method based on Dariusz’s answer: public static int getDigitCount(BigInteger number) { double factor = Math.log(2) / Math.log(10); int digitCount = (int) (factor * number.bitLength() + 1); if (BigInteger.TEN.pow(digitCount – 1).compareTo(number) > 0) { return digitCount – 1; } return digitCount; } The following code tests the numbers 1, 9, 10, 99, 100, … Read more
If you want to support arbitrarily big integers, it’s not safe to just do Math.log(bigInteger.doubleValue()); because this would fail if the argument exceeds the double range (about 2^1024 or 10^308, i.e. more than 300 decimal digits ). Here’s my own class that provides the methods double logBigInteger(BigInteger val); double logBigDecimal(BigDecimal val); BigDecimal expBig(double exponent); BigDecimal … Read more
Using the constructor BigInteger(String val) Translates the decimal String representation of a BigInteger into a BigInteger. Javadoc