减少 stl 向量的容量

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), and when 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 copy the 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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