了解C#中的嘶嘶声 [英] understanding the fizz buzz in C#

问题描述

在使用"while"循环解决C#中的"fizz-buzz"问题时，我发现首先应该找到3和5的倍数(15的倍数)，然后再像3和5的倍数一样以下.

When solving "fizz-buzz" in C# using a "while" loop, I found out that first I should find the multiples of both 3 and 5 (multiples of 15) and then go to the multiples of 3 and 5 like below.

int myval = 0;

while (myval < 100)
{
    myval = myval + 1;

    if (myval % 15 == 0)
    {
        listBox1.Items.Add("fizzbuzz");
    }
    else if (myval % 3 == 0)
    {
        listBox1.Items.Add("fizz");
    }
    else if (myval % 5 == 0)
    {
        listBox1.Items.Add("buzz");
    }
    else
    {
        listBox1.Items.Add(myval);
    }
}

但是，如果我编写代码先过滤3和5的倍数，然后转到3和5的倍数(15的倍数)，如下所示，最终结果只会显示嘶嘶声(3的倍数)和嗡嗡声( 5的倍数)而没有嘶嘶声(3和5的倍数).有谁知道这个IDE的原因是什么?

But if I write the code to filter multiples of 3 and 5 first and then go to the multiples of both 3 and 5 (multiples of 15) like below the end result only shows the fizz (multiples of 3) and buzz (multiples of 5) without fizz-buzz (multiples of both 3 and 5). Does anyone know what's the reason for this even IDE doesn't show me any errors.

myval = 0;

while (myval < 100)
{
    myval = myval + 1;

    if (myval % 3 == 0)
    {
        listBox1.Items.Add("fizz");
    }
    else if (myval % 5 == 0)
    {
        listBox1.Items.Add("buzz");
    }
    else if (myval % 15 == 0)
    {
        listBox1.Items.Add("fizzbuzz"); // for multiples of both 3 and 5  
    }
    else
    {
        listBox1.Items.Add(myval);
    }
}

推荐答案

这归结为if-else语句是按顺序处理的事实.一旦遇到求值为true的条件，就会跳过其他else if子句.

This boils down to the fact that if-else statements are processed sequentially. As soon as a condition that evaluates to true is encountered, the other else if clauses are skipped.

假设a和b均为true.当您写

if (a) {
    Foo1();
}
else if (b) {
    Foo2();
}

您不会同时执行Foo1和Foo2.因为a是true，所以执行Foo1甚至不评估b.

you do not execute both Foo1 and Foo2. Since a is true, Foo1 executes and b is not even evaluated.

现在考虑您的问题.考虑数字15.所有三个候选除数3、5和15均除以该数字.

Now consider your problem. Consider the number 15. All three candidate divisors, 3, 5 and 15, divide into that number.

if (myval % 3 == 0)
{
    listBox1.Items.Add("fizz");
}
else if (myval % 5 == 0)
{
    listBox1.Items.Add("buzz");
}
else if (myval % 15 == 0)
{
    listBox1.Items.Add("fizzbuzz"); // for multiples of both 3 and 5  
}
else
{
    listBox1.Items.Add(myval);
}

由于15的倍数也是3(和5)的倍数，因此您甚至都不会达到myval % 15 == 0的15倍数测试.

Since the multiples of 15 are also multiples of 3 (and 5), you will never even reach the myval % 15 == 0 test for multiples of 15.

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