On 28/05/2011, at 11:47 PM, Dmitri O.Kondratiev wrote:
Hello, I am trying to solve a simple task, but got stuck with double recursion - for some reason not all list elements get processed. Please advice on a simple solution, using plane old recursion :) *** Task: From a sequence of chars build all possible chains where each chain consists of chars that can be accessed from one to another. For example, given the sequence: "abcde" In table below chars in a left column can access a list of chars in the right column: a | b c d e b | c d e c | d e d | e
You have a set S of characters and a binary relation R ⊆ S × S and a chain is a sequence [x0,x1,...] such that x[0] ∈ S and for all i > 0, x[i-1] R x[i] Can a chain be empty? What constraints on R do you have that lead you to think that each chain is finite, or are you expecting infinite chains as well? (S = {a}, R = {(a,a)} admits chains of any length, including ones that do not terminate.)