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Expected length of the longest common subsequence for large alphabets

Publication at Faculty of Mathematics and Physics |
2005

Abstract

We consider the length L of the longest common subsequence of two randomly uniformly and independently chosen n character words over a k-ary alphabet. Subadditivity arguments yield that the expectation of L divided by n converges to a constant.

We prove a conjecture of Sankoff and Mainville from the early 80's giving the limit of this constant for k tending to infinity.