week3 kodutöö lahendus

Author: sim642

sols/week3/FiniteAutomaton.java

@@ -0,0 +1,122 @@
+package week3;
+
+import java.io.IOException;
+import java.nio.file.Paths;
+import java.util.*;
+
+public class FiniteAutomaton extends AbstractAutomaton {
+    private final Map<Integer, Map<Character, Set<Integer>>> transitions = new HashMap<>();
+    private Integer startState = null;
+    private final Set<Integer> acceptingStates = new HashSet<>();
+
+    @Override
+    public void addState(int state) {
+        transitions.put(state, new HashMap<>());
+    }
+
+    @Override
+    public void setStartState(int state) {
+        startState = state;
+    }
+
+    @Override
+    public void addAcceptingState(int state) {
+        acceptingStates.add(state);
+    }
+
+    @Override
+    public void addTransition(int fromState, Character label, int toState) {
+        Map<Character, Set<Integer>> fromMap = transitions.get(fromState);
+        Set<Integer> toSet = fromMap.computeIfAbsent(label, k -> new HashSet<>());
+        toSet.add(toState);
+    }
+
+    @Override
+    public Set<Integer> getStates() {
+        return transitions.keySet();
+    }
+
+    @Override
+    public Integer getStartState() {
+        return startState;
+    }
+
+    @Override
+    public Set<Integer> getAcceptingStates() {
+        return acceptingStates;
+    }
+
+    @Override
+    public Set<Character> getOutgoingLabels(int state) {
+        return transitions.get(state).keySet();
+    }
+
+    @Override
+    public Set<Integer> getDestinations(int state, Character label) {
+        return transitions.get(state).getOrDefault(label, Collections.emptySet());
+    }
+
+    @Override
+    public boolean accepts(String input) {
+        Set<Integer> currentStates = epsilonClosure(Collections.singleton(startState));
+        for (char c : input.toCharArray()) {
+            if (currentStates.isEmpty()) return false;
+            currentStates = move(currentStates, c);
+        }
+        return !Collections.disjoint(currentStates, acceptingStates);
+    }
+
+    // Defineerime abifunktsioon step, millega saab nii sulund kui ka move defineerida.
+    // See vaatab, kuhu võib etteantud tähega (muuhulgas epsiloniga) minna.
+    private Set<Integer> step(Set<Integer> states, Character c) {
+        Set<Integer> nextStates = new HashSet<>();
+        for (Integer state : states) nextStates.addAll(getDestinations(state, c));
+        return nextStates;
+    }
+
+    public Set<Integer> epsilonClosure(Set<Integer> states) {
+        Set<Integer> closure = new HashSet<>();
+        while (closure.addAll(states)) states = step(states, null);
+        return closure;
+        //return Fixpoints.closure(x -> step(x, null), states);
+    }
+
+    public Set<Integer> move(Set<Integer> states, Character c) {
+        return epsilonClosure(step(states, c));
+    }
+
+    /**
+     * Seda meetodit ei hinnata ja seda ei pea muutma, aga läbikukkunud testide korral
+     * antakse sulle automaadi kirjelduseks just selle meetodi tagastusväärtus.
+     */
+    @Override
+    public String toString() {
+        return "trans: " + transitions + "\n" +
+                "start: " + startState + ", end: " + acceptingStates;
+    }
+
+    static void main() throws IOException {
+        FiniteAutomaton fa = new FiniteAutomaton();
+
+        fa.addState(0);
+        fa.addState(1);
+        fa.addState(2);
+
+        fa.addTransition(0, 'b', 0);
+        fa.addTransition(0, 'c', 2);
+        fa.addTransition(2, 'a', 1);
+        fa.addTransition(1, 'd', 0);
+        fa.addTransition(0, null, 1);
+
+        fa.setStartState(0);
+        fa.addAcceptingState(1);
+
+        System.out.println(fa.accepts("cadbbbca")); // true
+        System.out.println(fa.accepts("abc"));      // false
+        System.out.println(fa.accepts(""));         // true
+
+        // Pead ise veenduda, et toString töötab...
+        System.out.println(fa);
+        fa.renderPngFile(Paths.get("graphs", "auto.png"));
+    }
+}