c语言三元运算符_了解C / C ++中的三元运算符

灰太狼 2023-02-28 08:40 99阅读 0赞

c语言三元运算符

In this article, we’ll take a look at understanding the ternary operator in C / C++.

在本文中，我们将了解C / C ++中的三元运算符。

The ternary operator (`? :`) is a very useful operator, which is very similar to if-else statements. This is a useful option for programmers, to avoid cluttering the code with nested if-else conditions.

三元运算符（ `? :` ：）是非常有用的运算符，它与if-else语句非常相似。 对于程序员来说，这是一个有用的选项，可以避免使用嵌套的if-else条件使代码混乱。

Let’s take a quick look at using this simple operator, using some illustrative examples!

让我们使用一些说明性示例快速浏览使用此简单运算符！

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## 三元运算符 **(****The Ternary Operator****)** ##

Before coming to the ternary operator, let’s look at the format for a simple `if-else` statement.

在使用三元运算符之前，让我们看一下简单的`if-else`语句的格式。

if (condition) {
        variable = expression1;
    }
    else {
        variable = expression2;
    }

While this is simple enough, it might be more convenient to write it in one line and assign to a `variable` directly!

尽管这很简单，但将其写成一行并直接分配给`variable`可能会更方便！

We can do this through the ternary operator.

我们可以通过三元运算符来实现。

The ternary operator works like this and is the same as the above `if-else` block.

三元运算符的工作方式与上面的`if-else`块相同。

variable = (condition != 0) ? expression1 : expression2;

See how simple it is?!

看看有多简单？！

What this says is that `variable` will be assigned the value of `expression1` if `condition` holds true. Otherwise, it will be given the value of `expression2`.

这表示如果`condition`成立，则将为`variable`分配`expression1`的值。 否则，它将被赋予`expression2`的值。

So, this is essentially the same as the original ‘if-else’ statement.

因此，这基本上与原始的“ if-else”语句相同。

Let’s now look at a simple example.

现在让我们看一个简单的例子。

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## 使用三元运算符-一些示例 **(****Using the Ternary Operator – Some Examples****)** ##

Consider the following program, which will assign variables to -1, based on whether it is odd or even.

考虑下面的程序，它将基于奇数还是偶数将变量分配给-1。

#include <stdio.h>
    
    int main() {
        int a = 10;
        int b = 5;
    
        int c = (a % 2 == 0) ? a : -1;
        int d = (b % 2 == 0) ? b : -1;
    
        printf("a = %d, c = %d\n", a, c);
        printf("b = %d, d = %d\n", b, d);
    
        return 0;
    }

**Output**

**输出量**

a = 10, c = 10
    b = 5, d = -1

As you can see, since a is even, the first part (after `?`) is now evaluated and assigned to c.

如您所见，由于a是偶数，因此现在将评估第一部分（在`?`之后）并将其分配给c。

While in the second case, since `b` is odd, the second part (after `:`) is now evaluated and assigned to d.

在第二种情况下，由于`b`为奇数，因此现在评估第二部分（在`:`之后）并将其分配给d。

Ternary operators also make writing recursive functions very easy to read.

三元运算符还使编写递归函数非常容易阅读。

Consider the below program, which uses a recursive function to find the fibonacci sequence, starting from 1, using ternary operators!

考虑下面的程序，该程序使用三元运算符从1开始使用递归函数查找斐波那契序列！

The recursive function will return 1 if `n <= 1`, and return `fib(n-1) + fib(n-1)` otherwise!

如果`n <= 1` ，则递归函数将返回1，否则将返回`fib(n-1) + fib(n-1)` ！

#include <stdio.h>
    
    int fibonacci(int n) {
        return (n <= 1) ? 1 : fibonacci(n-1) + fibonacci(n - 2);
    }
    
    int main() {
        int val = fibonacci(10);
        printf("Starting from 1, fibonacci(%d) = %d\n", 10, val);
        return 0;
    }

**Output**

**输出量**

Starting from 1, fibonacci(10) = 89

If you work it out, you can indeed verify that the 10th fibonacci number after 1 is 89.

如果计算出来，您确实可以验证1之后的第十个斐波那契数是89。

The recursive function is now a simple one-liner due to the ternary operator.

由于三元运算符，递归函数现在是一个简单的线性函数。

Hopefully, this gives you another reason to use ternary operators more often!

希望这为您提供了另一个更频繁使用三元运算符的理由！

--------------------

## 结论 **(****Conclusion****)** ##

We learned about using the Ternary operator (`? :`), which is a nifty trick using which we can avoid writing nested if-else conditions.

我们学习了如何使用三元运算符（ `? :` ：），这是一个不错的技巧，可以避免编写嵌套的if-else条件。

This makes writing simple conditional statements in a single line, which is a good option to have for C / C++ programmers.

这使得可以在一行中编写简单的条件语句，这对于C / C ++程序员是一个不错的选择。

## 参考资料 **(****References****)** ##

*  [Wikipedia Page][] on Ternary Operator
    
    有关三元运算符的[维基百科页面][Wikipedia Page]

--------------------

> 翻译自: [https://www.journaldev.com/40807/ternary-operator-in-c-plus-plus][https_www.journaldev.com_40807_ternary-operator-in-c-plus-plus]

c语言三元运算符

[Wikipedia Page]: https://en.wikipedia.org/wiki/%3F:
[https_www.journaldev.com_40807_ternary-operator-in-c-plus-plus]: https://www.journaldev.com/40807/ternary-operator-in-c-plus-plus