Sites
- https://leetcode.com/
- https://www.hackerrank.com/
- https://www.educative.io/
- https://interviewing.io/
- https://www.hackerearth.com/
- https://www.geeksforgeeks.org/
- https://www.interviewbit.com/
- https://www.algoexpert.io/product
Books
- Cracking the Coding Interview: 189 Programming Questions and Solutions
- Grokking Algorithms: An Illustrated Guide for Programmers and Other Curious People