[C++] upper_bound和lower_bound

upper_bound 源码

template <class ForwardIterator, class T>
ForwardIterator upper_bound (ForwardIterator first, ForwardIterator last, const T& val)
{
ForwardIterator it;
iterator_traits<ForwardIterator>::difference_type count, step;
count = std::distance(first,last);
while (count>0)
{
it = first; step=count/2; std::advance (it,step);
if (!(val<*it))                 // or: if (!comp(val,*it)), for version (2)
{ first=++it; count-=step+1;  }
else count=step;
}
return first;
}

lower_bound 源码

template <class ForwardIterator, class T>
ForwardIterator lower_bound (ForwardIterator first, ForwardIterator last, const T& val)
{
ForwardIterator it;
iterator_traits<ForwardIterator>::difference_type count, step;
count = distance(first,last);
while (count>0)
{
it = first; step=count/2; advance (it,step);
if (*it<val) {                 // or: if (comp(*it,val)), for version (2)
first=++it;
count-=step+1;
}
else count=step;
}
return first;
}