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
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
You need to add an assembly reference to System.Numerics.dll The MSDN entry on BigInteger states: BigInteger Structure … Namespace: System.Numerics Assembly: System.Numerics (in System.Numerics.dll)
I hope it’s not too late to answer this thread. You can try “LibTomMath” which is opensource and free (the author give away this project as public domain). It works out of the box without any configuration, just put all bn_*.c and tommath*.h to your Xcode project and you are ready to go. #import “tommath.h” … Read more
Using the constructor public BigInteger(String val) Translates the decimal String representation of a BigInteger into a BigInteger. Javadoc
There is no built-in “big number” support, but we can first check whether there is a larger integer kind available (as mentioned by Francescalus above and also many previous pages (e.g. this page). On my computer with gfortran-6.1, the compiler seems to support 128-bit integer kind, so I could calculate the result up to n=160 … Read more
Consider System.Numerics.BigInteger.
This image shows what you’re looking for. In your case it’s obviously larger numbers, but the principle stays the same. Examples of limits in java are: int: −2,147,483,648 to 2,147,483,647. long: -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807 In the image 0000, 0001 etc, shows the binary representation of the numbers. EDIT: In project euler you often have to … Read more
Just for fun: public static BigInteger sqrt(BigInteger x) { BigInteger div = BigInteger.ZERO.setBit(x.bitLength()/2); BigInteger div2 = div; // Loop until we hit the same value twice in a row, or wind // up alternating. for(;;) { BigInteger y = div.add(x.divide(div)).shiftRight(1); if (y.equals(div) || y.equals(div2)) return y; div2 = div; div = y; } }