The formulation of a merged sorted list from multiple input sorted lists in multiple phases using an array pair. Initially, the first array is contiguously populated with the input sorted lists. In the first phase, the first and second input sorted lists are merged into a first intermediary merged list within the second array. Each subsequent phase merges a prior intermediary merged list resulting from the prior phase and, a next input sorted list in the first array to generate a next intermediary merged list, or a merged sorted list if there or no further input in the first array. The intermediary merged lists alternate between the first array and the second array from one phase to the next phase.