归并排序

public static void merge(int[] numbers, int start, int mid, int end) {
    int i = start;
    int j = mid + 1;
    int k = 0;
    int[] sortedArr = new int[end - start + 1]; // 临时数组，用于存放排好序的下标从start到end的数据
    // 从start和mid+1开始，同时扫描进行排序
    while (i <= mid && j <= end) {
        if (numbers[i] < numbers[j]) sortedArr[k++] = numbers[i++];
        else sortedArr[k++] = numbers[j++];
    }

    // 当i（或者j）指针之一指向末尾，另一个指向的数据直接添加到排好序的末尾即可
    while (i <= mid) sortedArr[k++] = numbers[i++];
    while (j <= end) sortedArr[k++] = numbers[j++];

    for (i = 0; i < k; i++)
        numbers[start + i] = sortedArr[i];
}

public static void mergeSort(int[] numbers, int start, int end) {
    if (start < end) {
        // 从中间进行分割
        int mid = start + (end - start) /  2;
        mergeSort(numbers, start, mid);
        mergeSort(numbers, mid + 1, end);
        // 左右两边排好序以后再进行合并
        merge(numbers, start, mid, end);
    }
}


public static void main(String[] args) {
    int[] numbers = {3, 1, 2, 5, 4, 6, 9, 7, 10, 8};
    mergeSort(numbers, 0, numbers.length - 1);
    System.out.println(Arrays.toString(numbers));
}