Longest common subsequence: Difference between revisions

<lang Swift>func rlcs(_ s1: String, _ s2: String) -> String {

let x = s1.characters.count

let y = s2.characters.count

if x == 0 || y == 0 {

return ""

} else if s1[s1.startIndex.advancedByindex(xs1.startIndex, -offsetBy: x-1)] == s2[s2.startIndex.advancedByindex(ys2.startIndex, -offsetBy: y-1)] {

return rlcs(String(s1[s1.startIndex..<s1.startIndex.advancedByindex(xs1.startIndex, -offsetBy: x-1)]),

String(s2[s2.startIndex..<s2.startIndex.advancedByindex(ys2.startIndex, -offsetBy: y-1)])) + String(s1[s1.startIndex.advancedByindex(xs1.startIndex, -offsetBy: x-1)])

} else {

let xstr = rlcs(s1, String(s2[s2.startIndex..<s2.startIndex.advancedByindex(ys2.startIndex, -offsetBy: y-1)]))

let ystr = rlcs(String(s1[s1.startIndex..<s1.startIndex.advancedByindex(xs1.startIndex, -offsetBy: x-1)]), s2)

return xstr.characters.count > ystr.characters.count ? xstr : ystr

}

}</lang>