A New Method for Efficient in-Place Merging

There is a well-known simple, stable standard merge algorithm, which uses only linear time but for the price of double space. This extra space consumption has been often remarked as lack of the standard merge sort algorithm that covers a merge process as central operation. In-place merging is a way to overcome this lack and so is a topic with a long tradition of inspection in the area of theoretical computer science. We present an in-place merging algorithm that rear-ranges the elements to be merged by rotation, a special form of block interchanging. Our algorithm is novel, due to its technique of determination of the rotation-areas. Further it has a short and transparent definition. We will give a presentation of our algorithm and prove that it needs in the worst case not more than twice as much comparisons as the standard merge algorithm. Experimental work has shown that our algorithm is efficient and so might be of high practical interest.