add pancakesort

Author: KrishnaSSH

src/main/java/app/sort/PancakeSort.java

@@ -0,0 +1,27 @@
+package app.sort;
+
+import app.core.Ops;
+
+public class PancakeSort extends NamedSort {
+    public PancakeSort() { super("Pancake Sort"); }
+
+    @Override
+    public void generate(int[] a, Ops ops) {
+        for (int size = a.length; size > 1; size--) {
+            int maxIdx = 0;
+            for (int i = 1; i < size; i++) if (a[i] > a[maxIdx]) maxIdx = i;
+            if (maxIdx == size - 1) continue;
+            if (maxIdx > 0) flip(a, ops, maxIdx);
+            flip(a, ops, size - 1);
+        }
+    }
+
+    void flip(int[] a, Ops ops, int end) {
+        int i = 0, j = end;
+        while (i < j) {
+            ops.swap(a, i, j);
+            i++;
+            j--;
+        }
+    }
+}

src/main/java/app/sort/Sorts.java

@@ -25,6 +25,7 @@ private Sorts() {}
             new PigeonholeSort(),
             new CycleSort(),
             new BitonicSort(),
-            new ExternalMergeSort()
+            new ExternalMergeSort(),
+            new PancakeSort()
     );
 }