Binary search finds 1 in a million in 20 steps. Here's how.

追加: 2026-05-19

[00:00:00]You type a name into a search box. The app finds it instantly from a list of 1 million entries. How?

[00:00:06]It does not check every name. It starts in the middle. If your name comes before that midpoint alphabetically, everything after is gone. Half the list, one step.

[00:00:15]It jumps to the middle of what remains.

[00:00:17]Half again, one step.

[00:00:20]This is binary search. Every single step cuts the remaining candidates in half. 1 million entries takes at most 20 steps.

[00:00:27]1 billion takes 30.

[00:00:30]The catch, the list must be sorted.

[00:00:31]Without sorting, the middle tells you nothing. With sorting, it tells you everything.

[00:00:36]Full breakdown on the channel.