如何找到Java BigInteger的平方根？ [英] How can I find the Square Root of a Java BigInteger?

问题描述

是否有一个库可以找到BigInteger的平方根？我希望它离线计算 - 只计算一次，而不是在任何循环内。所以即使是计算量很大的解决方案也没关系。

Is there a library that will find the square root of a BigInteger? I want it computed offline - only once, and not inside any loop. So even computationally expensive solution is okay.

我不想找到一些算法和实现。一个现成的解决方案将是完美的。

I don't want to find some algorithm and implement. A readily available solution will be perfect.

推荐答案

只是为了好玩：

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;
    }
}

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