import java.util.Arrays;
/**
* 归并排序
*/
public class MergeSort implements IArraySort {
@Override
public int[] sort(int[] sourceArray) throws Exception {
// 对 arr 进行拷贝，不改变参数内容
int[] arr = Arrays.copyOf(sourceArray, sourceArray.length);
if (arr.length < 2) {
return arr;
}
int middle = (int) Math.floor(arr.length / 2);
int[] left = Arrays.copyOfRange(arr, 0, middle);
int[] right = Arrays.copyOfRange(arr, middle, arr.length);
return merge(sort(left), sort(right));
}
protected int[] merge(int[] left, int[] right) {
int[] result = new int[left.length + right.length];
int l = 0, r = 0, len = 0;
while (len < left.length + right.length) {
if (left[l] <= right[r]) {
result[len++] = left[l++];
if (l == left.length) {
for (int i = r; i < right.length; i++) {
result[len++] = right[r++];
}
}
} else {
result[len++] = right[r++];
if (r == right.length) {
for (int i = l; i < left.length; i++) {
result[len++] = left[l++];
}
}
}
}
return result;
}
}