initial commit

Sorting/MergeSorter.java

@@ -0,0 +1,64 @@
+package Sorting;
+
+public class MergeSorter extends Sorter{
+    
+    public MergeSorter(String filename){
+        super("merge",filename);
+    }
+
+    void sort(){
+        mergeSort(0,numbers.length-1);
+    }
+
+    void mergeSort(int leftIndex, int rightIndex){
+        if(compare(leftIndex,rightIndex)<0){
+            int middleIndex = (leftIndex+rightIndex)/2;
+            mergeSort(leftIndex,middleIndex);
+            mergeSort(middleIndex+1,rightIndex);
+            merge(leftIndex,middleIndex,rightIndex);
+        }
+    }
+
+    /**
+     * merges subarray from leftIndex...middleIndex with subarray from middleIndex+1...rightIndex
+     * @param leftIndex
+     * @param middleIndex
+     * @param rightIndex
+     */
+    void merge(int leftIndex, int middleIndex, int rightIndex){
+        int sizeLeft=middleIndex-leftIndex+1;//add 1 to include both endpoints
+        int sizeRight=rightIndex-middleIndex;//both endpoints already included, as middleIndex is part of left array
+        int[] left=new int[sizeLeft];
+        int[] right=new int[sizeRight];
+        for(int i=0;i<sizeLeft;i++){
+            left[i]=numbers[leftIndex+i];
+        }
+        for(int i=0;i<sizeRight;i++){
+            right[i]=numbers[middleIndex+1+i];
+        }
+        int i=0, j=0;//indices of left and right array
+        int k=leftIndex;//index of numbers array
+        while(i<sizeLeft&&j<sizeRight){
+            if(compare(left[i],right[j])<1){
+                numbers[k]=left[i];
+                i++;
+            }
+            else{
+                numbers[k]=right[j];
+                j++;
+            }
+            k++;
+        }
+        while(i<sizeLeft){
+            numbers[k]=left[i];
+            i++;
+            k++;
+        }
+        while(j<sizeRight){
+            numbers[k]=right[j];
+            j++;
+            k++;
+        }
+    }
+
+}