useful apps and websites for your preparation

Programming apps:

• SoloLearn
• Programming Hero
• Mimo
• Programming Hub
• Code Hub
• Grasshopper
• Enki
• Encode
• Codecademy
• DataCamp

Learning websites:

• W3School
• freeCodeCamp
• GeeksforGeeks
• Udacity
• Udemy, Inc.
• Codecademy
• Coursera
• Khan Academy
• edX

Queries Websites:

• Stack Overflow
• Quora
• Reddit
• CodeProject
• Programmers Heaven
• Coderanch
• FindNerd
• Chegg

Challenge Websites:

• Codewars
• HackerRank
• Topcoder
• Coderbyte
• HackerEarth
• Leetcode
• CodeChef
• Edabit
• Codeforces
• SPOJ

note: if you know any other websites and apps please let me know.. which can be helpful