For the recent Div 4 contest problem E (Romantic Glasses)
https://codeforces.net/contest/1915/problem/E
https://codeforces.net/contest/1915/submission/239539914 is TLE uses dict
whereas
https://codeforces.net/contest/1915/submission/239522644 passes uses set
I'm not sure why there would be this much difference in execution time.
Thanks for your time.