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Combining adjacent sorted runs within their existing array segment. A simple constant-auxiliary-space version moves the smaller second-run head before the first-run head by shifting the intervening block one place right. The finished prefix is always a merge of the consumed portions. This can use quadratic running time; minimizing storage does not automatically preserve the linear cost of a disjoint-output merge.

A contiguous nondecreasing segment of a sequence. Adjacent sorted runs can be merged in time linear in their combined lengths.