What are persistent data structures?

Persistent data structures are like toys that don’t get broken when you play with them, they stay just as good as new, even after many turns of the game.

Imagine you have a box of blocks. Every time you build something cool, like a castle or a tower, it stays there for everyone to see. But if you want to make a different shape, instead of knocking everything down and starting over, you just add more blocks on top, or maybe take some out from the side. The old buildings are still there; they’re just not in use anymore.

This is how persistent data structures work. They let you change things without losing what came before. Like having multiple versions of your toy castle, one with a tower, one with a bridge, and even one that’s completely different but still sitting beside the others.

When you use a normal box of blocks, if you want to change the shape of the building, you have to tear it all down. That’s like using a regular data structure, when you change something, the old version is gone forever.

But with a persistent data structure, each time you make a new shape, you keep the old one too. It’s like having many different castles side by side, they’re all built from the same blocks, but they look and feel completely different.