Using STL, I want to find the last instance of a certain value in a sequence.
This example will find the first instance of 0 in a vector of ints.
#include <algorithm>
#include <iterator>
#include <vector>
typedef std::vector<int> intvec;
intvec values;
// ... ints are added to values
intvec::const_iterator split = std::find(values.begin(), values.end(), 0);
Now I can use split
to do things to the subranges begin()
.. split
and split
.. end()
. I want to do something similar, but with split set to the last instance of 0. My first instinct was to use reverse iterators.
intvec::const_iterator split = std::find(values.rbegin(), values.开发者_C百科rend(), 0);
This doesn't work because split
is the wrong type of iterator. So ...
intvec::const_reverse_iterator split = std::find(values.rbegin(), values.rend(), 0);
But the problem now is that I can't make "head" and "tail" ranges like begin(), split
and split, end()
because those aren't reverse iterators. Is there a way to convert the reverse iterator to the corresponding forward (or random access) iterator? Is there a better way to find the last instance of an element in the sequence so that I'm left with a compatible iterator?
But the problem now is that I can't make "head" and "tail" ranges using begin() and end() because those aren't reverse iterators.
reverse_iterator::base()
is what you are looking for - section new members on SGIs reverse_iterator description or here on cppreference.com
What about std::find_end? (To find the last occurrence of a sequence)
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