Hash tables for three methods. Three methods to find genome positions of 1-mismatch from the subsequence AAGT. Genome position 1000 is ACGT, which is the 1-mismatch of the subsequence. The first method refers to the hash table 16 times. The second method refers to the table just once, but the table is 16-fold larger. The third method refers to the table three times. After getting position 1002 from the hash table, the method elongates the alignment toward the front of the sequence.