std::inplace_merge

 

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all_of any_of none_of (C++11) (C++11) (C++11) for_each count count_if mismatch equal	find find_if find_if_not (C++11) find_end find_first_of adjacent_find search search_n
Modifying sequence operations
copy copy_if (C++11) copy_n (C++11) copy_backward move (C++11) move_backward (C++11) fill fill_n transform generate generate_n remove remove_if remove_copy remove_copy_if	replace replace_if replace_copy replace_copy_if swap swap_ranges iter_swap reverse reverse_copy rotate rotate_copy random_shuffle shuffle   (C++11) unique unique_copy
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is_partitioned (C++11) partition partition_copy (C++11)	stable_partition partition_point (C++11)
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is_sorted (C++11) is_sorted_until (C++11) sort	partial_sort partial_sort_copy stable_sort nth_element
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lower_bound upper_bound	binary_search equal_range
Set operations (on sorted ranges)
merge inplace_merge includes	set_difference set_intersection set_symmetric_difference set_union
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is_heap is_heap_until (C++11) make_heap	push_heap pop_heap sort_heap
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C library
qsort	bsearch

 

Defined in header <algorithm>
template< class BidirectionalIterator > void inplace_merge( BidirectionalIterator first,                     BidirectionalIterator middle,                     BidirectionalIterator last );	(1)
template< class BidirectionalIterator, class Compare> void inplace_merge( BidirectionalIterator first,                     BidirectionalIterator middle,                     BidirectionalIterator last,                     Compare comp );	(2)

Merges two consecutive sorted ranges [first, middle) and [middle, last) into one sorted range [first, last). The order of equal elements is guaranteed to be preserved. The first version uses operator< to compare the elements, the second version uses the given comparison function comp.

Parameters

first	-	the beginning of the first sorted range
middle	-	the end of the first sorted range and the beginning of the second
last	-	the end of the second sorted range
comp	-	comparison function which returns ​true if the first argument is less than the second. The signature of the comparison function should be equivalent to the following: bool cmp(const Type1 &a, const Type2 &b); The signature does not need to have const &, but the function must not modify the objects passed to it. The types  Type1 and  Type2 must be such that an object of type BidirectionalIterator can be dereferenced and then implicitly converted to both of them. ​

Return value

(none)

Complexity

Exctly N-1 comparisons if enough additional memory is available, otherwise N·log(N) where N = std::distance(first, last).

Example

The following code is an implementation of merge sort.

#include <vector>
#include <iostream>
#include <algorithm>
 
template<class Iter>
void merge_sort(Iter first, Iter last)
{
    if (last - first > 1) {
        Iter middle = first + (last - first) / 2;
        merge_sort(first, middle);
        merge_sort(middle, last);
        std::inplace_merge(first, middle, last);
    }
}
 
int main()
{
    std::vector<int> v{8, 2, -2, 0, 11, 11, 1, 7, 3};
    merge_sort(v.begin(), v.end());
    for(auto n : v) {
        std::cout << n << ' ';
    }
    std::cout << '\n';
}

Output:

-2 0 1 2 3 7 8 11 11

See also

merge	merges two sorted ranges (function template)
sort	sorts a range into ascending order (function template)
stable_sort	sorts a range of elements while preserving order between equal elements (function template)