C ++向量插入& push_back差异 [英] C++ vector's insert & push_back difference

问题描述

我想知道向量的 push_back 和 insert 函数。

是否有结构差异？

是否有很大的性能差异？

Is there a really big performance difference(s)?

推荐答案

最大的区别是它们的功能。 push_back 总是在向量和的末尾插入一个新元素insert 允许您选择新元素的位置。这会影响性能。 向量元素只有在需要增加它的长度时才会在内存中移动，因为分配的内存太少。另一方面， insert 强制移动新元素的所选位置之后的所有元素。你只需要为它做一个地方。这就是为什么 insert 可能通常不如 push_back 有效。

The biggest difference is their functionality. push_back always puts a new element at the end of the vector and insert allows you to select new element's position. This impacts the performance. vector elements are moved in the memory only when it's necessary to increase it's length because too less memory was allocated for it. On the other hand insert forces to move all elements after the selected position of a new element. You simply have to make a place for it. This is why insert might often be less efficient than push_back.

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