For ordinary difference sets problem , It can be used set To solve , May refer to
https://blog.csdn.net/bitcarmanlee/article/details/51622263
But for Form like
a = [1, 2, 3, 3, 4]
b = [1, 3]
Their difference is actually not c = [2, 4], It is [2, 3, 4]
Double layer pairwise comparison is required
The code is simple , But in reality, we should pay attention to the distinction
for num in b:
if num in a:
a.remove(num)
return a
