Wolf, sheep, cabbage is a logic puzzle, in which the player (boatman) has to transport a wolf, a sheep and a cabbage from one river bank to the other. In the game the player must obey these rules:

  • The player can use a boat to transport the objects, but he may take at maximum one thing with him every time.
  • If the sheep remains unguarded on the same bank as the cabbage, than the sheep will eat the cabbage.
  • If the wolf remains unguarded on the same bank as the sheep, than the wolf will eat the sheep.

Solution

From the algorithmic point of view the puzzle can be easily solved by a backtracking algorithm. The backtracking algorithm in every step tries to transport one thing to the other bank and then it checks the consistency of the partial solution. If the solution is consistent, than it repeats the step (transports another thing). If not, than the backtracking algorithm returns to the preceding decision and changes it (transports something else, or returns to the previous decision, if all possible objects were already tried out). Using this technique of organized trials and failures the algorithm finds the solution.

Code

    /**
     * Solves the sheep-cabbage-wolf riddle and prints out its solution
     */
    public static void solveSheepCabbageWolf(){
        sheepCabbageWolf(false, false, false, false, new LinkedList<String>());
    }
    /**
     * Solves the sheep-cabbage-wolf riddle and prints out its solution (the actual worker method)
     * @param sheep true if the sheep is on the right bank, false otherwise
     * @param cabbage true if the cabbage is on the right bank, false otherwise
     * @param wolf true if the wolf is on the right bank, false otherwise
     * @param farmer true if the farmer (boat) is on the right bank, false otherwise
     * @param solution partial solution
     * @return false if the partial solution is invalid
     */
    private static boolean sheepCabbageWolf(boolean sheep, boolean cabbage, boolean wolf, boolean farmer, Deque<String> solution) {
        if (sheep && cabbage && wolf && farmer) {
            printSolution(solution);
            return true;
        }
        if (!checkConsistency(sheep, cabbage, wolf, farmer)) {
            return false;
        }
        if (solution.isEmpty() || !solution.peek().equals("boatman")) {
            solution.addFirst("boatman");
            if (sheepCabbageWolf(sheep, cabbage, wolf, !farmer, solution)) {
                return true;
            }
            solution.pop(); //backtrack
        }           
        if (sheep == farmer && (solution.isEmpty() || !solution.peek().equals("sheep"))) {
            solution.addFirst("sheep");
            if (sheepCabbageWolf(!sheep, cabbage, wolf, !farmer, solution)) {
                return true;
            }
            solution.pop(); //backtrack
        }
        if (cabbage == farmer && (solution.isEmpty() || !solution.peek().equals("cabbage"))) {
            solution.addFirst("cabbage");
            if (sheepCabbageWolf(sheep, !cabbage, wolf, !farmer, solution)) {
                return true;
            }
            solution.pop(); //backtrack
        }
        if (wolf == farmer && (solution.isEmpty() || !solution.peek().equals("wolf"))) {
            solution.addFirst("wolf");
            if (sheepCabbageWolf(sheep, cabbage, !wolf, !farmer, solution)) {
                return true;
            }
            solution.pop(); //backtrack
        }     
        return false;
    }

    /**
     * Check consistency of the partial solution
     * @param sheep if the sheep is on the right bank, false otherwise
     * @param cabbage if the cabbage is on the right bank, false otherwise
     * @param wolf if the wolf is on the right bank, false otherwise
     * @param farmer if the farmer is on the right bank, false otherwise
     * @return true if the solution is consistent, false otherwise
     */
    private static boolean checkConsistency(boolean sheep, boolean cabbage, boolean wolf, boolean farmer) {
        if (sheep == cabbage && sheep != farmer) {
            return false;
        } else if (sheep == wolf && sheep != farmer) {
            return false;
        }
        return true;
    }

    /**
     * Prints out the solution of the sheep-cabbage-wolf problem
     * @param solution 
     */
    private static void printSolution(Deque<String> solution) {
        while (!solution.isEmpty()) {
            System.out.print(solution.pollLast() + " ");
        }
        System.out.println();
    }
% farmer, sheep, cabbage, wolf                            
start :- transport(left, left, left, left, empty, X).

opposite(left, right).
opposite(right, left).

safe(X, X, X).
safe(X, Y, Z) :- X \\= Y.

transport(right, right, right, right, _, []).

transport(F, K, Z, V, B, X) :- 
  B \\= empty, 
  opposite(F, F2), 
  safe(K, Z, F2), 
  safe(K, V, F2), 
  transport(F2, K, Z, V, empty, X1),
  append([farmer], X1, X).   

transport(F, K, Z, V, B, X) :- 
  F == V, 
  B \\= wolf, 
  opposite(F, F2), 
  opposite(V, V2), 
  safe(K, V2, F2), 
  safe(K, Z, F2),    
  transport(F2, K, Z, V2, wolf, X1),
  append([wolf], X1, X). 

transport(F, K, Z, V, B, X) :- 
  F == K, 
  B \\= sheep, 
  opposite(F, F2), 
  opposite(K, K2), 
  safe(K2, Z, F2), 
  safe(K2, V, F2), 
  transport(F2, K2, Z, V, sheep, X1),
  append([sheep], X1, X). 

transport(F, K, Z, V, B, X) :- 
  F == Z, 
  B \\= cabbage, 
  opposite(F, F2), 
  opposite(Z, Z2), 
  safe(K, Z2, F2), 
  safe(K, V, F2), 
  transport(F2, K, Z2, V, cabbage, X1),
  append([cabbage], X1, X). 

SEO od společnosti Digital Pylon


Online casino s algoritmem

České casino online online slot-vegas.cz

Hrajte nejlepší hry jako je GoodGame Empire.





Zajímavé články: Jak najít práci snů? Zvolte kariéru v IT!, Češi mají rádi hrací automaty online, Jak funguje algoritmické obchodování Casino, Online výuka Algoritmus a online marketing mají svá pravidla, Automaty, Matematický vliv, Ratings, Jak fungují algoritmy hazardních her online: více znalostí, více peněz, SYPWAI - nástroj pro vědecký vývoj, Vynikají na globálním trhu: Nejlepší vývojáři softwaru pro online výherní automaty, Jak si vybrat nejlepší české online casino, Proč byste měli hrát online casino VPN revoluce, Kde najdeme algoritmy v každodenním životě?, Čeká vás pracovní pohovor mimo město? Podívejte se, jak dokonale zvládnout včasný příchod, 5 úžasných technologií ze světa hazardních her, Mirror and access to Mostbet, Svou kancelář můžete mít stále po ruce, Jaké výhody má digitalizovaná firma oproti off-line konkurenci?, Jaký systém vybrat pro snadné řízení výroby?, Nahradí umělá inteligence ajťáky?, Důvody, proč používat SnapTik ke stahování videí TikTok, Dokonalý den na pláži: Co si vzít s sebou, aby byl výlet zábavný a bezpečný?, Jak přežít dlouhý let?, Go pay GoodGame Empire, Blockchain, Rozhovor, Umělá inteligence


Doporučujeme

Internet pro vaši firmu na míru

https://www.algoritmy.net