sizeof() 一个向量

2021-12-21 00:00:00 vector c++ sizeof

我有一个 vector> 数据结构(事务数据库),我想知道它的大小.当我对每个 set 使用 sizeof() 时,尽管集合包含 3、4 或 5 个字符,但大小为 24.后来,当我将 sizeof() 与 vector 一起使用时,> 大小是 12...我想这不是知道数据结构大小的方法.有什么帮助吗?谢谢.

I have a vector<set<char> > data structure (transactions database) and I want to know the size of it. When I use sizeof() with each set<char> the size is 24 in spite of the set contains 3, 4 or 5 chars. Later, when I use sizeof() with the vector<set<char> > the size is 12... I suppose this is not the way to know the size of a data structure. Any help? Thanks.

推荐答案

你想要 vector::size()set::size().

假设 v 是您的向量,请执行以下操作:

Assuming v is your vector, do this:

size_t size = 0;
for (vector<set<char> >::const_iterator cit = v.begin(); cit != v.end(); ++cit) {
    size += cit->size();
}

sizeof()sizeof(char) 的倍数(通常为一个字节)为您提供它所应用的对象/类型的内存大小.如果你想知道容器及其元素的内存大小,你可以这样做:

sizeof() is giving you the in-memory size of the object/type it is applied to, in multiples of sizeof(char) (usually one byte). If you want to know the in-memory size of the container and its elements, you could do this:

sizeof(v) + sizeof(T) * v.capacity();//其中 T 是元素类型

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