Difference between end of a container and iterator pointing to an item inside. C++

Question

list<int> l;
list<int>::iterator start;
list<int>::iterator end;
list<int>::iterator mid;
for (int i = 0; i < 100; ++i)
    l.push_back(i);
start= l.begin();
end= l.end();
mid = start+ (end- start) / 2;
cout << *mid << endl;

Okay I have a concrete example now. end- start does not compile.

Did you intend to write ble.begin() + (ble.begin() - ble.end()) / 2 or was it supposed to be ble.begin() + (ble.end() - ble.begin()) / 2 ? — Adrian Panasiuk
– Adrian Panasiuk, Commented Nov 16, 2013 at 0:23
What do you mean it doesn't work? Doesn't compile? Doesn't give you the result you want? — user1508519
– user1508519, Commented Nov 16, 2013 at 0:24
I think he literally means last - start / 2, so start/2 obviously doesn't compile. — Adrian Panasiuk
– Adrian Panasiuk, Commented Nov 16, 2013 at 0:25

billz · Accepted Answer · 2013-11-16 00:29:36Z

3

list iterator is Bidirectional iterator, it's notRandom access iterator. You can't calloperator-` on it.

you could just try to use std::advance to move your iterator to the middle of container

std::advance(ble.begin(), ble.size()/2);

answered Nov 16, 2013 at 0:29

billz

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