Fig. 1.

Illustration of the iterative algorithm to enumerate k-mer frequencies. For the k ^′-mer $a_1\cdots a_{k^{\prime }}$, its two frequency slots with zero counts for nucleotides c and t are removed to obtain (k ^′+1)-mers $a_1\cdots a_{k^{\prime }}$a and $a_1\cdots a_{k^{\prime }}$g