This paper provides an efficient method to find all feasible offsets for a given separation in a single-layer channel routing problem. With n nets, c columns, and c = O(n), the algorithm runs in time O(n 1.5 lg n), which improves upon the more straightforward O(n 2 ) approach. (Results for river routing do not apply, since we allow single-sided nets.) As a corollary of this result, the optimal offset (the one that minimizes separation) can be found in O(n 1.5 lg 2 n) time. We also provide

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... s for the case in which c = O(n). In addition, we achieve better running times for the cases in which there are no two-sided nets or all single-sided nets are on one side of the channel.