vector.back() 和 vector[vector.size() - 1] 之间的区别？

Question

Is there any difference between calling vector.back() and vector[vector.size() - 1] with std::vector 's?

Answer 1

vector.back() is simpler to read and write. Also, more containers offer c.back() than c[c.size() - 1] , which is important for generic code.

In a debug-runtime, both are equally likely to be trapped on empty containers, nor is the resulting code and thus their performance when using optimization expected to differ significantly.

Answer 2

vector.back() is one function call and shorter to write: It is simpler. vector[vector.size() - 1] is two function calls and a subtraction, and longer to write: It is more complex.

Behaviourally, they are the same for std::vector . However back is more generic, and can be used with all standard bidirectional containers ( std::forward_list being the only standard container that doesn't support it). operator[] is only supported by random access containers.