Persistent data structures

Persistent data structures are special kinds of data structures that help us keep track of information. Unlike regular data structures, which store information once, a persistent data structure keeps track of all the changes made to it over time. This means that if you change something in the data structure, the original information is still available and can be accessed even after the changes have been made. It's like taking a family photo album. You can rearrange the sequence of the photos, but the original photo album is still there.