C++ Algorithm Library - inplace_merge() Function

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Description

The C++ function std::algorithm::inplace_merge() merges two sorted sequence in-place. It uses binary function; for comparison.

Declaration

Following is the declaration for std::algorithm::inplace_merge() function form std::algorithm header.

C++98

template <class BidirectionalIterator, class Compare>
void inplace_merge (BidirectionalIterator first, BidirectionalIterator middle,
   BidirectionalIterator last, Compare comp);

Parameters

• first − Bidirectional iterator to the initial position of the first sequence.

• middle − Bidirectional iterator to the initial position of the second sequence.

• last − Bidirectional iterator to the past-the-end position of the second sequence.

• comp − A binary function which accepts two argument and returns bool.

Return value

None

Exceptions

Throws exception if element comparison or swap operation or an operation on an iterator throws exception.

Please note that invalid parameters cause undefined behavior.

Time complexity

Linear.

Example

The following example shows the usage of std::algorithm::inplace_merge() function.

#include <iostream>
#include <algorithm>
#include <vector>

using namespace std;

bool descending_sort(int a, int b) {
   return (a > b);
}

int main(void) {
   vector<int> v = {3, 1, 5, 4, 2};

   inplace_merge(v.begin(), v.begin() + 2, v.end(), descending_sort);

   for (auto it = v.begin(); it != v.end(); ++it)
      cout << *it << endl;

   return 0;
}

Let us compile and run the above program, this will produce the following result −

5
4
3
2
1