In-place merge sort, based on C++ STL's stable_sort(). O(N log<sup>2</sup> N) time complexity, O(1) space complexity, stable. Much slower than plain old mergeSort(), so only use it if you really need the O(1) space.
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In-place merge sort, based on C++ STL's stable_sort(). O(N log<sup>2</sup> N) time complexity, O(1) space complexity, stable. Much slower than plain old mergeSort(), so only use it if you really need the O(1) space.