本文介绍了检查BigInteger是不是一个完美的正方形的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
我有一个BigInteger值,假设它是282并且在变量x中。我现在想写一个while循环,声明:
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: a ← a + 1 b2 ← a*a - N endwhile我将如何使用BigInteger做这样的事情?
How would I do such a thing using BigInteger?
编辑:这样做的目的是为了写一个此方法。正如文章所述,必须检查b2是否不是正方形。
The purpose for this is so I can write this method. As the article states one must check if b2 is not square.
推荐答案计算整数平方根,然后检查它的正方形是你的号码。这是我使用 Heron方法计算平方根的方法:
Compute the integer square root, then check that its square is your number. Here is my method of computing the square root using Heron's method:
private static final BigInteger TWO = BigInteger.valueOf(2); /** * Computes the integer square root of a number. * * @param n The number. * * @return The integer square root, i.e. the largest number whose square * doesn't exceed n. */ public static BigInteger sqrt(BigInteger n) { if (n.signum() >= 0) { final int bitLength = n.bitLength(); BigInteger root = BigInteger.ONE.shiftLeft(bitLength / 2); while (!isSqrt(n, root)) { root = root.add(n.divide(root)).divide(TWO); } return root; } else { throw new ArithmeticException("square root of negative number"); } } private static boolean isSqrt(BigInteger n, BigInteger root) { final BigInteger lowerBound = root.pow(2); final BigInteger upperBound = root.add(BigInteger.ONE).pow(2); return lowerBoundpareTo(n) <= 0 && npareTo(upperBound) < 0; }更多推荐
检查BigInteger是不是一个完美的正方形
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