Site where can we find the best algorithmic strategies?

Algos, strategies, code
1
2

you can check this link. https://zerodha.com/expert-advisors/ 

3

You can check www.wisestocktrader.com, it contains many strategies developed by active traders.

4

Check out the below link:

http://tradingtuitions.com/category/categories/amibroker/trading-systems/