ReverseOrder

import random
import copy
def GenerateRandomList(number, size):
	temp = []
	random_legth = random.randint(0, size)
	current_length = 0
	while current_length < random_legth:
		temp.append(random.randint(1, number))
		current_length += 1
	return temp
    
def ReverseOrder(arr):
    if arr is None or len(arr) < 2:
        return 0
    return SortProcess(arr, 0, len(arr) - 1)

def SortProcess(arr, L, R):
    if L == R:
        return 0
    mid = (L + R) // 2
    return  SortProcess(arr, L, mid) + SortProcess(arr, mid + 1, R) + Merge(arr, L, mid, R)

def Merge(arr, L, mid, R):
    help_list = []
    p1 = L
    p2 = mid + 1
    res = 0
    while p1 <= mid and p2 <= R:
        if arr[p1] > arr[p2]:
            res += 1 * (mid - p1 + 1)
            help_list.append(arr[p2])
            p2 += 1
        else:
            help_list.append(arr[p1])
            p1 += 1
            

    while p1 <= mid:
        help_list.append(arr[p1])
        p1 += 1

    while p2 <= R:
        help_list.append(arr[p2])
        p2 += 1

    for i in range(len(help_list)):
        arr[L + i] = help_list[i]

    return res


def standard_ReverseOrder(arr):
	ans = 0
	for i in range(len(arr) - 1):
		for j in range(i+1, len(arr)):
			if arr[i] > arr[j]:
				ans += 1
	return ans

for i in range(100):
	l = GenerateRandomList(100,100)
	temp = copy.copy(l)
	standard_l = standard_ReverseOrder(l) % 1000000007
	res = ReverseOrder(l) % 1000000007
	if res != standard_l:
		print(temp)
print('Done!')