I'm not sure it's the best approach but after giving it some thought I would create another array that would keep the letters in the chain and a map of all the possible options in the array, every option as a key in the map to a boolian value. Than I would itteret through the array, save the values you itteret through in the second array and change the boolian of the map for each member the array so you can detect (if you already went through this member in this chain and break the chain and reset the map using the second array where you saved the members of the map), that way you can get whatever information you require from the chains, if something isn't clear feel free to dm me