Check if BigInteger is not a perfect square

Question

I have a BigInteger value, let\'s say it is 282 and is inside the variable x. I now want to write a while loop that states:

while b2 isn\'t a perfect square:         


        

Answer 1

I use this:

SQRPerfect is the number I want to test: This also has a nice Square Root so you get to use this as well if you need it seperately. You can get a little speed up if you bring the Square Root inside the Perfect Square test, but I like having both functions.

if(PerfectSQR(SQRPerfect)){
    Do Something
}


public static Boolean PerfectSQR(BigInteger A) {
    Boolean p=false;
    BigInteger B=SQRT(A);
    BigInteger C=B.multiply(B);
    if (C.equals(A)){p=true;}
    return p;
}

public static BigInteger SQRT(BigInteger A) {
    BigInteger a=BigInteger.ONE,b=A.shiftRight(5).add(BigInteger.valueOf(8));
    while ((b.compareTo(a))>=0){
        BigInteger mid = a.add(b).shiftRight(1);
        if (mid.multiply(mid).compareTo(A)>0){b=mid.subtract(BigInteger.ONE);}
        else{a=mid.add(BigInteger.ONE);}
    }
  return a.subtract(BigInteger.ONE);
}