#!/usr/bin/ruby

#
## https://rosettacode.org/wiki/Longest_common_subsequence#Sidef
#

func lcs(String xstr, String ystr) is cached -> String {
    (xstr.is_empty || ystr.is_empty) && return '';

    var(x, xs, y, ys) = (xstr.first, xstr.slice(1),
                         ystr.first, ystr.slice(1));

    if (x == y) {
        x + lcs(xs, ys)
    } else {
        [lcs(xstr, ys), lcs(xs, ystr)].max_by {|x| x.len };
    }
}

assert_eq(lcs("thisisatest", "testing123testing"), "tsitest");

say "** Test passed!";