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Task/Sorting-algorithms-Merge-sort/Java/sorting-algorithms-merge-sort.java

@@ -0,0 +1,53 @@
+import java.util.List;
+import java.util.ArrayList;
+import java.util.Iterator;
+
+public class Merge {
+    public static <E extends Comparable<? super E>> List<E> mergeSort(List<E> m) {
+        if (m.size() <= 1) return m;
+
+        int middle = m.size() / 2;
+        List<E> left = m.subList(0, middle);
+        List<E> right = m.subList(middle, m.size());
+
+        right = mergeSort(right);
+        left = mergeSort(left);
+        List<E> result = merge(left, right);
+
+        return result;
+    }
+
+    public static <E extends Comparable<? super E>> List<E> merge(List<E> left, List<E> right) {
+        List<E> result = new ArrayList<E>();
+        Iterator<E> it1 = left.iterator();
+        Iterator<E> it2 = right.iterator();
+
+	E x = it1.next();
+	E y = it2.next();
+        while (true) {
+            //change the direction of this comparison to change the direction of the sort
+            if (x.compareTo(y) <= 0) {
+		result.add(x);
+		if (it1.hasNext())
+		    x = it1.next();
+		else {
+		    result.add(y);
+		    while (it2.hasNext())
+			result.add(it2.next());
+		    break;
+		}
+	    } else {
+		result.add(y);
+		if (it2.hasNext())
+		    y = it2.next();
+		else {
+		    result.add(x);
+		    while (it1.hasNext())
+			result.add(it1.next());
+		    break;
+		}
+	    }
+        }
+        return result;
+    }
+}