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问题描述
有没有办法减少向量的容量?
Is there a way to reduce the capacity of a vector ?
我的代码将值插入到一个向量中(事先不知道它们的编号)，并且完成后，向量仅用于读取操作.
My code inserts values into a vector (not knowing their number beforehand), andwhen this finishes, the vectors are used only for read operations.
我想我可以创建一个新的向量，用大小做一个 .reseve() 并复制项目，但我真的不喜欢额外的复制操作.
I guess I could create a new vector, do a .reseve() with the size and copythe items, but I don't really like the extra copy operation.
PS:我不关心便携式解决方案，只要它适用于 gcc.
PS: I don't care for a portable solution, as long as it works for gcc.
推荐答案
std::vector<T>(v).swap(v);
用另一个向量交换内容会交换容量.
Swapping the contents with another vector swaps the capacity.
std::vector<T>(v).swap(v); ==> is equivalent to
std::vector<T> tmp(v); // copy elements into a temporary vector
v.swap(tmp); // swap internal vector data
Swap() 只会改变内部数据结构.
Swap() would only change the internal data structure.
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