C++ In a Nutshell

Name

adjacent_find function template — Searches for a pair of adjacent, equal items

Synopsis

template<typename FwdIter>
  FwdIter adjacent_find(FwdIter first, FwdIter last);
template<typename FwdIter, typename BinaryPredicate>
  FwdIter adjacent_find(FwdIter first, FwdIter last, BinaryPredicate pred);

The adjacent_find function template looks for the first set of adjacent items in the range [first, last) that are equal (first version) or in which pred(*iter, *(iter+1)) is true (second version). Items are “adjacent” when their iterators differ by one position.

The return value is an iterator that points to the first of the adjacent items, or last if no matching items are found. See Figure 13-1 for an example.

Figure 13-1. Using adjacent_find to find two adjacent, equivalent items

Technical Notes

The adjacent_find function template returns i, in which i = first + n, and n is the smallest value such that *(first + n) == *(first + n + 1) and first + n + 1 < last, or, if there is no such n, i = last.

Complexity is linear: the standard is muddled, but any reasonable implementation calls the predicate (operator== or pred) exactly n + 1 times.

See Also

find function template, find_if function template