模运算符如何工作？ [英] How does the modulus operator work?

问题描述

假设我需要格式化数组的输出，以便每行显示固定数量的元素。我如何使用模数运算？

Let's say that I need to format the output of an array to display a fixed number of elements per line. How do I go about doing that using modulus operation?

使用C ++，下面的代码每行显示6个元素，但我不知道如何和为什么它的工作原理？

Using C++, the code below works for displaying 6 elements per line but I have no idea how and why it works?

for ( count = 0 ; count < size ; count++)
{
    cout << somearray[count];
    if( count % 6 == 5) cout << endl;
}

如果我想要每行显示5个元素怎么办？如何在C ++表达式中找到所需的确切表达式？

What if I want to display 5 elements per line? How do i find the exact expression needed?

推荐答案

a％b 返回a除以b的余数（如果它们是正的，对于负数，结果的符号是实现定义的）。例如：

in C++ expression a % b returns remainder of division of a by b (if they are positive. For negative numbers sign of result is implementation defined). For example:

5 % 2 = 1
13 % 5 = 3

有了这些知识，我们可以尝试理解你的代码。条件 count％6 == 5 表示当除以6的余数为5时，将写入换行符。这是多久发生一次？正确的6行（练习：写数字1..30，下划线满足这个条件），从第6行开始（计数= 5）。

With this knowledge we can try to understand your code. Condition count % 6 == 5 means that newline will be written when remainder of division count by 6 is five. How often does that happen? Exactly 6 lines apart (excercise : write numbers 1..30 and underline the ones that satisfy this condition), starting at 6-th line (count = 5).

要从代码中获得所需的行为，应该将条件更改为 count％5 == 4 ，从第5行开始，每5行将有一行换行= 4）。

To get desired behaviour from your code, you should change condition to count % 5 == 4, what will give you newline every 5 lines, starting at 5-th line (count = 4).

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