将数组的所有元素初始化为 C++ 中的一个默认值? [英] Initialization of all elements of an array to one default value in C++?

问题描述

C++ Notes: Array Initialization 有一个很好的列表数组的初始化.我有一个

int array[100] = {-1};

期望它充满 -1 但它不是，只有第一个值是，其余是 0 与随机值的混合.

代码

int array[100] = {0};

工作正常并将每个元素设置为 0.

我在这里遗漏了什么.. 如果值不为零，就不能初始化它吗?

和 2:默认初始化(如上)是否比通常的遍历整个数组并赋值的循环快，还是做同样的事情?

解决方案

使用您使用的语法，

int array[100] = {-1};

说将第一个元素设置为 -1，其余的设置为 0"，因为所有省略的元素都设置为 0.>

在 C++ 中，要将它们全部设置为 -1，您可以使用类似 std::fill_n(来自):

std::fill_n(array, 100, -1);

在便携式 C 中，您必须滚动自己的循环.有编译器扩展，或者你可以依赖实现定义的行为作为捷径(如果可以的话).

C++ Notes: Array Initialization has a nice list over initialization of arrays. I have a

int array[100] = {-1};

expecting it to be full with -1's but its not, only first value is and the rest are 0's mixed with random values.

The code

int array[100] = {0};

works just fine and sets each element to 0.

What am I missing here.. Can't one initialize it if the value isn't zero ?

And 2: Is the default initialization (as above) faster than the usual loop through the whole array and assign a value or does it do the same thing?

解决方案

Using the syntax that you used,

int array[100] = {-1};

says "set the first element to -1 and the rest to 0" since all omitted elements are set to 0.

In C++, to set them all to -1, you can use something like std::fill_n (from <algorithm>):

std::fill_n(array, 100, -1);

In portable C, you have to roll your own loop. There are compiler-extensions or you can depend on implementation-defined behavior as a shortcut if that's acceptable.

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