将数组的所有元素初始化为C++中的一个默认值?
C++ Notes: Array Initialization 有一个很好的列表数组的初始化.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，只有第一个值是，其余的都是 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.
我在这里遗漏了什么.如果值不为零，就不能初始化它吗?
What am I missing here.. Can't one initialize it if the value isn't zero ?
还有 2:默认初始化(如上)是否比通常循环遍历整个数组并赋值更快，还是做同样的事情?
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
使用你使用的语法，
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，您可以使用类似 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，或者如果可以接受的话，您可以依赖实现定义的行为作为捷径.
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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