Vim search and replace based on surrounding text

Question

How do I replace vector with std::vector if and only if vector is not already preceded by std::? I could maybe come up with a convoluted way of doing it but I want something simple.

Answer 1

Using negative lookbehind. This will replace vector with std::vector if and only if vector is not already preceded by std::

:%s/\v(std::)@<!vector/std::vector/g