Question

Given a collection of actions and userIds an error occurs when a userId takes a specific action in order for example. Preferably in Javascript. Python or Java is okay too.

A => B => => C gives an errror
B => A => C no error and etc

Write a function that takes in a list of (Actions, UserIds) pairs and returns the user Id that ecounters the error

Sample Input:

action_user_1 = [
["A", "1"],
["B", "1"],
["B", "2"],
["C", "1"],
["C", "2"],
["C", "3"],
["A", "2],
["A", "3"],
["A", "2"],
["B", "2],
["C", "2"],
]

Expected output 1,2

action_user_2 = [
["A", "1"],
["A", "1"]
["A", "1"]
["B", "1"],
["B", "2"],
["C", "2"],
["C", "2"],
["C", "3"],
["A", "2],
["A", "3"],
["A", "2"],
["B", "2],
["C", "2"],
]

Expected output 2

Answer 1

def ErrorUsers(action_user):
  '''
  Returns the error userids
  '''
  uniq_user = set() #unique userids
  error = []
  for lst in action_user: #for each userid
    uniq_user.add(lst[1]) #add into a set to get unique values
  for user in uniq_user: #for each user
    u=[]
    for lst in action_user: #for each action list
      if user == lst[1]: #if user == action user
        u.append(lst[0]) #append the action
    new=''.join(u) #make a string by joining the characters within a action list u
    if 'ABC' in new: #if ABC in order present then error user append
      error.append(user)
    elif 'BC' in new: #if BC in order present then error user append
       error.append(user)
  return error #return the error user list


if __name__ == "__main__":
  action_user_1 = [
  ["A", "1"],
  ["B", "1"],
  ["B", "2"],
  ["C", "1"],
  ["C", "2"],
  ["C", "3"],
  ["A", "2"],
  ["A", "3"],
  ["A", "2"],
  ["B", "2"],
  ["C", "2"],
  ]
  print(action_user_1)
  print("Error users: ",','.join(ErrorUsers(action_user_1)))
  action_user_2 = [
  ["A", "1"],
  ["A", "1"],
  ["A", "1"],
  ["B", "1"],
  ["B", "2"],
  ["C", "2"],
  ["C", "2"],
  ["C", "3"],
  ["A", "2"],
  ["A", "3"],
  ["A", "2"],
  ["B", "2"],
  ["C", "2"],
  ]
  print(action_user_2)
  print("Error users: ",','.join(ErrorUsers(action_user_2)))

Output:

Though I write comment with each line if you have any doubt you can ask in the comment. Thanks.