ELI5: Explain Like I'm 5

ALL (complexity)

All, also known as "Big O" notation, is a way to measure how long it takes to solve a problem using a computer program.

It's like playing a game of hide and seek. If you have to find someone who is hiding in a small room with very few hiding spots, it will be easy and fast to find them. But if they're hiding in a big park with lots of hiding spots, it will take longer to find them. In the same way, some problems are easy and quick for a computer program to solve, while others are much harder and take more time.

All helps us measure how long it will take a computer program to solve a problem. It's like a way to predict how long the program will have to look for the solution. This is important because we want to write programs that solve problems as quickly as possible.

All uses special symbols like "O(n)" or "O(n^2)" to represent how long it takes for a program to solve a problem. The "n" in these symbols represents the size of the problem, or how many pieces of data the program has to search through.

For example, if we want to find a word in a dictionary, it would take a different amount of time depending on how many words are in the dictionary. If there are only 10 words, it would be easy to find the word we're looking for. But if there were 10,000 words, it would take longer to find the word.

Using All, we can measure how long it would take a computer program to search for a word in a dictionary of any size. If the program takes "O(n)" time, it means that the time it takes to find the word scales linearly with the size of the dictionary. If the program takes "O(n^2)" time, it means that the time it takes to find the word scales with the square of the size of the dictionary.

So when we're writing computer programs, we use All to help us predict how long it will take for the program to solve a problem. We want to make sure that the program runs as quickly and efficiently as possible, and All helps us do that.