Expand-around-center linear-time palindrome counting:
for c = 0 to 2*n - 2 do
let l = ref (c / 2) in
let r = ref ((c + 1) / 2) in
while !l >= 0 && !r < n && s.[!l] = s.[!r] do
count := !count + 1; l := !l - 1; r := !r + 1
done
done
The 2n-1 centers cover both odd (c even -> l = r) and even
(c odd -> l = r - 1) palindromes.
For "aabaa":
5 singletons + 2 "aa" + 1 "aba" + 1 "aabaa" = 9
Complements lps_dp.ml (longest subsequence) and manacher.ml
(longest substring); this one *counts* all palindromic substrings.
187 baseline programs total.
giles
d3340107e6