Palindromic Tree/Err Tree:
Resource :
https://www.facebook.com/groups/341771679363942/permalink/1424558271085272
https://www.youtube.com/watch?v=PAz0WTvldss&list=PLv0QPiaV6CZsUiM0fa0WDLOUiio9jxvfB&index=11
Practice :
Merge Sort Tree:
Resource :
Practice :