使 Java 的模数表现得像负数一样的最佳方法? [英] Best way to make Java's modulus behave like it should with negative numbers?

问题描述

在java中当你这样做

In java when you do

a % b

如果 a 是负数，它将返回一个负结果，而不是像它应该的那样环绕到 b.解决此问题的最佳方法是什么?我唯一能想到的就是

If a is negative, it will return a negative result, instead of wrapping around to b like it should. What's the best way to fix this? Only way I can think is

a < 0 ? b + a : a % b

推荐答案

它的行为应该是 a % b = a - a/b * b;即它是余数.

It behaves as it should a % b = a - a / b * b; i.e. it's the remainder.

你可以做 (a % b + b) % b

You can do (a % b + b) % b

这个表达式的作用是(a % b)的结果必然低于b，无论a是正数还是负数.添加 b 处理 a 的负值，因为 (a % b) 是 -b和0，(a % b + b)必然低于b而为正.最后一个模数是在 a 开始时为正数的情况下存在的，因为如果 a 是正数 (a % b + b) 会变大比 b.因此， (a % b + b) % b 再次将其变成小于 b (并且不会影响负的 a 值).

This expression works as the result of (a % b) is necessarily lower than b, no matter if a is positive or negative. Adding b takes care of the negative values of a, since (a % b) is a negative value between -b and 0, (a % b + b) is necessarily lower than b and positive. The last modulo is there in case a was positive to begin with, since if a is positive (a % b + b) would become larger than b. Therefore, (a % b + b) % b turns it into smaller than b again (and doesn't affect negative a values).

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