X = "ACGGTTA"  (m=7)   Y = "CGTAT"  (n=5)

  c table:
        j:    0   1   2   3   4   5
          y:    -   C   G   T   A   T
  i=0 x=-     0   0   0   0   0   0
  i=1 x=A     0   0   0   0   1   1
  i=2 x=C     0   1   1   1   1   1
  i=3 x=G     0   1   2   2   2   2
  i=4 x=G     0   1   2   2   2   2
  i=5 x=T     0   1   2   3   3   3
  i=6 x=T     0   1   2   3   3   4
  i=7 x=A     0   1   2   3   4   4

  b table  ( \ = copy, ^ = skip x, < = skip y ):
          j:    C   G   T   A   T
  i=1 x=A       ^   ^   ^   \   <
  i=2 x=C       \   <   <   ^   ^
  i=3 x=G       ^   \   <   <   <
  i=4 x=G       ^   \   ^   ^   ^
  i=5 x=T       ^   ^   \   <   \
  i=6 x=T       ^   ^   \   ^   \
  i=7 x=A       ^   ^   ^   \   ^

  LCS length          = 4
  one LCS             = "CGTT"
  two-row variant     = 4 (same length, no string)

m=n       LCS len       full ms       full MiB        2-row ms      2-row MiB     
200       124           0.28          0.308           0.03          0.002         
1000      645           6.36          7.645           0.74          0.008         
4000      2598          247.23        122.131         25.07         0.031         
8000      5216          1930.83       488.403         152.86        0.061
