Iterating over a vector in reverse direction

Question

I need to iterate over a vector from the end to the beginnig. The \"correct\" way is

for(std::vector::reverse_iterator rit = v.rbegin(); rit !=          


        

Answer 1

There's nothing to stop your reverse_iterator loop also using the index as described in multiple other answers. That way you can use the iterator or index as needed in the // do the work part, for minimal extra cost.

size_t index = v.size() - 1;
for(std::vector<SomeT>::reverse_iterator rit = v.rbegin(); 
    rit != v.rend(); ++rit, --index)
{
  // do the work
}

Though I'm curious to know what you need the index for. Accessing v[index] is the same as accessing *rit.

Answer 2

I think that:

for(unsigned i = v.size() - 1; i >= 0; --i)

is fine if you check

!v.empty()

earlier.

Answer 3

to be aesthetically pleasing! ;)

for(unsigned i = v.size() - 1; v.size() > i; --i)