# Binary Search: so simple your child has done it

I wasn't a Computer Science major. That is to say, I'm not the kind of person who would probably have had algorithms on the brain. When I got to Coding Boot Camp we covered Algorithms, Data Structures, and the like. I did, however, find algorithms interesting. The word 'algorithms' alone was enough to make me feel anxious at first (as many multisyllabic words do). They turned out to be a great way to learn about how to approach the code I would later write. 

## What's this thing do?
I realized one search algorithm is something we innately do as children: Binary Search. "Binary" means that it's referring to two things. A binary question would be one where there are only two reasonable responses, say a "yes" or "no" for instance. So Binary Search will have something to do with two states (while you haven't found what you're looking for): before or after.

My four-year-old has even demonstrated how intuitive this algorithm is. My daughter was looking for a certain part of a book she likes. So here's what I saw my four-year-old do:

```
Open the storybook to an arbitrary place
	while she has not found what she's looking for:
		Look at the pictures to see where she was in the story
	       if it's before that, look to the left in the book
	       else look to the right
```

Not too complicated. You've probably done this every time you pick up a real dictionary or phone book. That's basically all Binary Search is, except for two requirements:

1. The items you are searching through have to be sorted.
2. You always look at the middle of whatever is left in your search, not an arbitrary value.

## Is it worth it?
That's what the process basically looks like. Now, let's play a game. I'm going to pick a number between 1 and 1,000. It's going to be 1,000. Let's try it as a sequential search, that's where you start at the beginning and check each one in order. In the worst-case scenario, you will have to guess every number to find it. That's maybe a thousand guesses and a loss in the faith of everyone that you have mind-reading abilities. With that same game, it would take something like 10 moves to find what you're looking for with Binary Search. Ten guesses out of a thousand options are far better, efficiency-wise, than guessing each number until you get it. 

Put a different way: How would you rather look up words in the dictionary? One word at a time? Or is it faster to open the book and see if you found it the first time and adjust your search? Binary Search is something you already do a version of.