New to Open Source? You can start contributing to this repo.
Check out current issues and contribute to them. You can send as many Pull Requests as you want!
Some of the basic algorithms - Linear Search, Binary Search, Sorting, Sieve, DP algorithms etc. Some of data structures are mentioned in README of DS folder.
You can also contribute to problem solutions of problems available on various platforms like Codeforces, Codechef, Hackerrank, Hackerearth, Atcoder, Topcoder, CS Academy, Leetcode, SPOJ, Interviewbit etc.