An improved optimal algorithm for bubble-sorting-based non-Manhattan channel routing

It is well known that a non-Manhattan channel router always uses fewer routing tracks than a Manhattan router in a channel. To our knowledge, for a bubble-sorting-based non-Manhattan channel routing (BSNMCR) problem, Chaudhary's O(kn/sup 2/) heuristic algorithm (1991) and Chen's O(k/sup 2/n) optimal algorithm (1994) have been, respectively, proposed, where it is the number of terminals and k is the number of routing tracks in a channel. However, the time complexity of the two algorithms is in O(n/sup 3/) time in the worst case. In this paper, based on optimality-oriented swap-direction selection in an optimal bubble-sorting solution, an improved optimal algorithm for a BSNMCR problem is proposed, and the time complexity of the proposed algorithm is proven to be in O(kn) time and in O(n/sup 2/) time in the worst case.