使Java模数的行为与负数一样的最佳方法是什么？ [英] Best way to make Java's modulus behave like it should with negative numbers?

问题描述

在你做的时候

a % b

如果a是负数，它将返回负结果，而不是像它应该的那样回绕到b。解决这个问题的最佳方法是什么？我能想到的只有

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

它表现得像应该a％b = a - a / b * b;即它是剩余部分。

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

此表达式的作用是（a％b）必然低于 b ，无论 a 是正还是负。添加 b 负责 a 的负值，因为（a％b）是 -b 和 0 之间的负值，（a ％b + b）必然低于 b 且为正数。最后一个模数是在 a 开始时为正，因为如果 a 为正（a％b + b）将大于 b 。因此，（a％b + b）％b 再次将其变为小于 b （并且不会影响否定 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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