I tried to make a function , using iterators, to walk a deque backward and my function does not work . I would appreciate if somebody cna help me :
double Dq_Iter_Backward()
{
deque<int>::reverse_iterator InvDeqIter;
DeqIter=intdeq.begin();
InvDeqIter = intdeq.end()-1;
for(InvDeqIter = intdeq.end()-1;InvDeqIter!=intdeq.begin()-1;--DeqIter)
{
cout<<InvDeqIter;
}
elapsed = clock()- start_time;
elapsed_time = elapsed / ((double) CLOCKS_PER_SEC);
return elapsed_time;
}
A couple things:
I think you meant --InvDeqiter instead of --DeqIter
otherwise the for loop will likely be never ending as the stop conditional relates to InvDeqIter not DeqIter.
To read a deque or a double ended list backward using a reverse_iterator you increment the reverse iterator, not decrement it. You could decrement a bidirectional iterator to read backward if you wanted to. I believe an iterator without any prefix, like increment_iterator or reverse_iterator, is a bidirectional iterator. Traditionally I would use rbegin() and rend() when working with reverse_iterators, because of decreased risk of off by one errors. For example, in your code if you change --instead of
intdeq.end()-1;
I would use
intdeq.rbegin();
Last, but not least, if you are trying to see what ints are in intdeq you don't want this:
cout<<InvDeqIter;
which outputs the address in InvDeqIter, you want this:
cout << *InvDeqIter;
which dereferences the iterator to the information held at the address in the iterator.
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