optimize swapBlocks and scramble

Author: cicirello

src/main/java/org/cicirello/permutations/Permutation.java

@@ -539,10 +539,12 @@ public void scramble(int i, int j, RandomGenerator r) {
     if (i == j) {
       return;
     }
-    int k = j;
+    int k;
     if (i > j) {
       k = i;
       i = j;
+    } else {
+      k = j;
     }
     boolean changed = false;
     for (; k > i + 1; k--) {
@@ -745,12 +747,12 @@ public void swapBlocks(int a, int b, int i, int j) {
       // blocks are adjacent
       removeAndInsert(i, j - i + 1, a);
     } else {
-      int[] temp = new int[j - a + 1];
+      int[] temp = new int[j - b];
       int k = j - i + 1;
       System.arraycopy(permutation, i, temp, 0, k);
       int m = i - b - 1;
       System.arraycopy(permutation, b + 1, temp, k, m);
-      System.arraycopy(permutation, a, temp, k + m, b - a + 1);
+      System.arraycopy(permutation, a, permutation, a + temp.length, b - a + 1);
       System.arraycopy(temp, 0, permutation, a, temp.length);
       hashCodeIsCached = false;
     }