Code after lecture

src/main/java/sorting/MergeSort.java

+package sorting;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+public class MergeSort implements Sorter{
+
+	@Override
+	public <T extends Comparable<? super T>> void sort(List<T> list) {
+		if(list.size()<=2) { //O(1)
+			if(list.size()==2) {
+				if(list.get(0).compareTo(list.get(1))>0) {
+					Collections.swap(list, 0, 1);
+				}
+			}
+			return;
+		}
+		//divide
+		int mid = list.size()/2; //O(1)
+		ArrayList<T> first = new ArrayList<T>(list.subList(0, mid)); //O(n)
+		ArrayList<T> last = new ArrayList<T>(list.subList(mid, list.size())); //O(n)
+		
+		//recurse
+		sort(first); 
+		sort(last);
+		
+		//conquer
+		int i=0;
+		int j=0;
+		int index=0;
+		while(i<first.size() && j<last.size()) {//n iterations O(1)
+			if(first.get(i).compareTo(last.get(j))<0) {
+				list.set(index, first.get(i));
+				i++;
+			}
+			else {
+				list.set(index, last.get(j));
+				j++;
+			}
+			index++;
+		}
+		while(i<first.size()) {
+			list.set(index, first.get(i));
+			i++;
+			index++;
+		}
+
+		while(j<last.size()) {
+			list.set(index, last.get(j));
+			j++;
+			index++;
+		}
+}
+
+}

src/test/java/sorting/SorterTest.java

@@ -25,9 +25,9 @@ class SorterTest {
 		toTest = new ArrayList<Sorter>();
 		toTest.add(new JavaSort());
 		//toTest.add(new SelectionSort());
-		toTest.add(new InsertionSort());
+		//toTest.add(new InsertionSort());
 		toTest.add(new QuickSort());
-		//toTest.add(new MergeSort());
+		toTest.add(new MergeSort());
 		inputStrings = RandomListGenerator.generateStrings(1000000); 
 	}