Hashtags used only once

tags holds the hashtags that one person has used in their posts so far, in the order they were used. The # sign in front of each hashtag is left out.

Complete the function solution, which returns a list of the hashtags that were used exactly once, in the order they appear in tags. If there is no such hashtag, return an empty list.

Function

solution(tags)

Constraints

• The length of tags is from 1 to 100,000.
• Each hashtag is a string of lowercase English letters and digits, with a length from 1 to 20.

Examples

Starter code

def solution(tags):
    answer = []
    return answer