归并排序

def merge_sort(array):
    """
    归并排序,将数组分为左右两部分,然后先对两部分分别进行归并排序.
    归并排序完成后,左右将各有序,然后建立一个新的用来储存结果的数组,遍历左右部分,依次将最小的树加到新数组中
    :param array:
    :return:
    """
    if len(array) == 1:
        return array

    i = len(array) // 2
    array_1 = merge_sort(array[:i])
    array_2 = merge_sort(array[i:])
    new_array = []
    for k in array_1:
        m = 0
        for j in array_2:
            if k > j:
                m += 1
                new_array.append(j)
            else:
                break

        array_2 = array_2[m:]
        new_array.append(k)

    for k in array_2:
        new_array.append(k)

    return new_array


a = [1, 5, 3, 2, 45, 23, 1, 78, 214, 56, 3213, 54, 812]
print('归并排序:', merge_sort(a))
a.sort()
print('系统排序:', a)