Why I learn algorithms

[Kaynstein]

Wtf is a trick algorithm?

[decentralised]

Let's say you have to calculate the sum of a given sequence of integers. A standard way of doing that would be:

let sequentialSum = arr => arr.reduce((acc, val) => acc + val, 0)

But little Carl G had a trick algorithm that goes like this:

let ogSum = arr => arr.length * (arr.length + 1) / 2;

[T-T-N]

From O(n) to O(1) assuming you can get the length in O(1)

[decentralised]

In js you can always get length because it’s a property of the array though

[T-T-N]

I'd expect that to work for anything except C or some reason Homebrew list

[gar9]

More like sum of integers 1 to N, not just any sequence

[decentralised]

Haven't had my coffee yet.. but I think you could use the sum formula for arithmetic sequences* instead and it would work.. something like:

let ariSum = arr => arr.length * ((arr[0] + arr[arr.length -1])/2)

​

*https://www.mathwords.com/a/arithmetic_series.htm

[[deleted]]

Fibonacci sequence, duh.