Segment Tree
In plain terms
A tree for fast range queries and updates over an array.
Going deeper
A segment tree stores aggregate values (sums, mins) over array ranges, answering range queries and point updates in logarithmic time. It's a competitive-programming staple.
Under the hood
Supports range queries/updates in O(log n); lazy propagation enables efficient range updates.
Examples
Range sum/min queries, interval problems, competitive programming.
Think of it like...
Like nested summary folders, each holding the total for a section, so you total any range fast.