C++ 向量::清除
时间：2023-10-07问题描述
vector <weight> decoy;
void clear_decoy() {
decoy.clear();
vector<weight> (decoy).swap(decoy);
}
在上面的方法clear_decoy()中，vector 是什么意思?
In the above method clear_decoy(), what does vector<weight> (decoy).swap(decoy); mean please?
该方法是否清除decoy?谢谢！
Does the method clear decoy or not? Thanks!
推荐答案
它创建一个新的 Weight 对象向量(将为空)并与 decoy 交换.
It creates a new vector of Weight objects (which will be empty) and swaps it with decoy.
这样做的原因是默认情况下，std::vector
The reason for this is that by default, std::vector<t>::clear often doesn't actually reduce the storage used by a vector, it merely destroys all the objects contained there. This way, the vector has room to store more objects without reallocation in the future.
但是，有时您想修剪向量中的容量.与新创建的向量(它一直存在到它的行尾，因此在那里被销毁)交换会释放向量分配的所有内存.
Sometimes, however, you want to trim the capacity in the vector. Swapping with a newly created vector (which lives until the end of it's line, and is therefore destroyed there) frees all the memory allocated by the vector.
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