归并排序

public class MergeSort {

    public static void mergeSort(int array[], int start, int end) {
        if (start >= end) {
            return;
        }
        int mid = (end - start) / 2 + start;
        mergeSort(array, start, mid);
        mergeSort(array, mid + 1, end);
        merge(array, start, mid, end);
    }

    public static void merge(int array[], int start, int mid, int end) {

        int length = end - start + 1;
        int temp[] = new int[length];
        int left = start;
        int mid1 = mid + 1;
        int i = 0;
        while (left <= mid && mid1 <= end) {
            if (array[left] < array[mid1]) {
                temp[i++] = array[left++];
            } else {
                temp[i++] = array[mid1++];
            }

        }

        while (left <= mid) {
            temp[i++] = array[left++];
        }
        while (mid1 <= end) {
            temp[i++] = array[mid1++];
        }

        for (int n = 0; n < length; n++) {
            array[n + start] = temp[n];
        }
    }

    public static void main(String[] args) {
        int a[] = { 1, 51, 23, 4, 6, 9, 9, 10, 55 };
        mergeSort(a, 0, a.length - 1);
        System.out.println(Arrays.toString(a));
    }

}