67 lines
2.0 KiB
Java
67 lines
2.0 KiB
Java
package net.abhinavsarkar.algorist.sort;
|
|
|
|
import java.lang.reflect.Array;
|
|
import java.util.Arrays;
|
|
import net.abhinavsarkar.algorist.Sorter;
|
|
|
|
public class MergeSorter<T> implements Sorter<T>
|
|
{
|
|
@Override
|
|
public T[] sort(T[] input, Comparator<T> comparator)
|
|
{
|
|
if (input.length == 0) {
|
|
return input;
|
|
}
|
|
return this.sort(input, 0, input.length, comparator);
|
|
}
|
|
|
|
private T[] sort(T[] input, int start, int end, Comparator<T> comparator)
|
|
{
|
|
if (start == end - 1) {
|
|
T[] output = mkArray(input, 1);
|
|
output[0] = input[start];
|
|
return output;
|
|
}
|
|
|
|
int half = start + (end - start)/2;
|
|
T[] left = this.sort(input, start, half, comparator);
|
|
T[] right = this.sort(input, half, end, comparator);
|
|
return this.merge(left, right, comparator);
|
|
}
|
|
|
|
private T[] merge(T[] left, T[] right, Comparator<T> comparator)
|
|
{
|
|
T[] output = mkArray(left, left.length + right.length);
|
|
int i, j, k;
|
|
i = j = k = 0;
|
|
while (i < left.length || j < right.length) {
|
|
if (i >= left.length) {
|
|
System.arraycopy(right, j, output, j + left.length, right.length - j);
|
|
break;
|
|
}
|
|
if (j >= right.length) {
|
|
System.arraycopy(left, i, output, i + right.length, left.length - i);
|
|
break;
|
|
}
|
|
output[k++] = comparator.compare(left[i], right[j]) <= 0 ? left[i++] : right[j++];
|
|
}
|
|
|
|
return output;
|
|
}
|
|
|
|
@SuppressWarnings("unchecked")
|
|
private T[] mkArray(T[] input, int length)
|
|
{
|
|
return (T[]) Array.newInstance(input.getClass().getComponentType(), length);
|
|
}
|
|
|
|
public static void main(String[] args)
|
|
{
|
|
Sorter<String> sorter = new MergeSorter<>();
|
|
String[] sorted =
|
|
sorter.sort(new String[]{"abhinav", "sarkar", "barista", "jordan", "data"},
|
|
(s, anotherString) -> anotherString.compareTo(s));
|
|
System.out.println(Arrays.toString(sorted));
|
|
}
|
|
}
|