Leetcode Hackerrank Geeks for geeks Firecode? Obviously others Personally I like leetcode because the tagging but hackerrank has problems that try to teach you/refresh you on concepts which is neat.
InterviewBit
Lintcode
LeetCode for what companies will ask for real.
Leetcode.
Practice onsites: IBM, Microsoft, Amazon, Cisco
IBM and Cisco ask technical questions?
No, just a way to practice breathing and making sure you can sustain a pulse for several hours.