C++ In a Nutshell

Name

merge function template — Merges sorted ranges

Synopsis

template<typename InIter1, typename InIter2, typename OutIter>
  OutIter merge(InIter1 first1, InIter1 last1, InIter2 first2, InIter2 last2,
                OutIter result); 
template<typename InIter1, typename InIter2, typename OutIter, typename Compare>
  OutIter merge(InIter1 first1, InIter1 last1, InIter2 first2, InIter2 last2,
                OutIter result, Compare comp);

The merge function template merges the sorted ranges [first1, last1) and [first2, last2), copying the results into the sequence that starts with result. You must ensure that the destination has enough room for the entire merged sequence.

The return value is the end value of the destination iterator, that is, result + (last1 - first1) + (last2 - first2).

The destination range must not overlap either of the input ranges.

The merge is stable, so elements preserve their relative order. Equivalent elements are copied, so elements from the first range come before elements from the second range.

The first form compares values using the < operator. The second form calls comp(*iter1, *iter2).

Technical Notes

Let length1 = last1 - first1 and length2 = last2 - first2.

Precondition: !(*(i + 1) < *i) for all i in [first1, last1 - 1) and !(*(j + 1) < *j) for all j in [first2, last2 - 1).

Postcondition: !(*(i + 1) < *i) for all i in [result, result + length1 + length2 - 1).

Complexity is linear: at most, length1 + length2 - 1 comparisons are performed.

See Also

inplace_merge function template, sort function template ...