Get Path "R+D"

func getPath(_ n : Int) -> Set<String>{
    var res = Set<String>()
    getPathDFS(n , n , "", &res)

    return res
}


func getPathDFS(_ n : Int, _ m : Int, _ curr: String, _ res: inout  Set<String>){
    if n == 0 && m == 0{
        res.insert(curr)
        return
    }
    if n > 0 {
        getPathDFS( n - 1, m, curr + "d", &res)
    }
    if m > 0 {
        getPathDFS( n , m - 1, curr + "r", &res)
    }
}