Data commit

Task/Topswops/Java/topswops.java

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+public class Topswops {
+    static final int maxBest = 32;
+    static int[] best;
+
+    static private void trySwaps(int[] deck, int f, int d, int n) {
+        if (d > best[n])
+            best[n] = d;
+
+        for (int i = n - 1; i >= 0; i--) {
+            if (deck[i] == -1 || deck[i] == i)
+                break;
+            if (d + best[i] <= best[n])
+                return;
+        }
+
+        int[] deck2 = deck.clone();
+        for (int i = 1; i < n; i++) {
+            final int k = 1 << i;
+            if (deck2[i] == -1) {
+                if ((f & k) != 0)
+                    continue;
+            } else if (deck2[i] != i)
+                continue;
+
+            deck2[0] = i;
+            for (int j = i - 1; j >= 0; j--)
+                deck2[i - j] = deck[j]; // Reverse copy.
+            trySwaps(deck2, f | k, d + 1, n);
+        }
+    }
+
+    static int topswops(int n) {
+        assert(n > 0 && n < maxBest);
+        best[n] = 0;
+        int[] deck0 = new int[n + 1];
+        for (int i = 1; i < n; i++)
+            deck0[i] = -1;
+        trySwaps(deck0, 1, 0, n);
+        return best[n];
+    }
+
+    public static void main(String[] args) {
+        best = new int[maxBest];
+        for (int i = 1; i < 11; i++)
+            System.out.println(i + ": " + topswops(i));
+    }
+}