Github user yufcuy commented on the issue:
https://github.com/apache/commons-lang/pull/189
Hello, @britter @kinow
The details of Levenshtein distance can be find at
https://en.wikipedia.org/wiki/Levenshtein_distance, as it describe, the
algorithm is compute a matrix to hold the Levenshtein distances between all
prefixes of the first string and all prefixes of the second. For all i and j,
d[i][j] will hold the Levenshtein distance between the first i characters of s
and the first j characters of t.
The previous impl use two matrix rows for the construction. When we
calculate the value of d[i][j] we find only the value of d[i-1][j-1], d[i-1][j]
and d[i][j-1] are used according to the algorithm. And we use a matrix row p[]
for the construction, when calculate p[j] at the ith iteration, it actually
calculate the value of d[i][j], and only d[i-1][j-1] is covered by p[j-1], so
we use variable 'upper_left' to hold d[i-1][j-1], and use variable 'upper' to
hold next 'upper_left'.
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