在C ++中将数组的所有元素初始化为一个默认值? [英] Initialization of all elements of an array to one default value in C++?

问题描述

C ++注意:数组初始化有一个不错的清单数组的初始化.我有一个

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

int array[100] = {-1};

期望它充满-1，但不是，只有第一个值为，其余为0与随机值混合.

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.

代码

int array[100] = {0};

工作正常，并将每个元素设置为0.

works just fine and sets each element to 0.

我在这里缺少什么.如果值不为零，无法初始化吗?

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

和2:默认的初始化(如上所述)是否比遍历整个数组并分配值的常规循环要快?或者它执行相同的操作?

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?

推荐答案

使用您使用的语法，

int array[100] = {-1};

表示将第一个元素设置为-1，其余元素设置为0"，因为所有省略的元素都设置为0.

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

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

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

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，或者如果可以接受，您可以依赖实现定义的行为作为快捷方式.

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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