Ranking and unranking algorithms for loopless generation of t-ary trees

In this paper, we present two new ranking and unranking algorithms for z-sequences in Gray-code order. These algorithms are designed based on a loopless generation algorithm which is given for z-sequences corresponding to t-ary trees by Roelants van Baronaigien and Xiang et al. Up to our knowledge no other ranking and unranking algorithms are given for Gray-codes corresponding to t-ary trees. The time complexity of both algorithms for t-ary trees with n nodes is O(n²t).