https://www.youtube.com/playlist?list=PLgUwDviBIf0rENwdL0nEH0uGom9no0nyB

https://www.youtube.com/playlist?list=PLgUwDviBIf0pMFMWuuvDNMAkoQFi-h0ZF

https://leetcode.com/tag/array/

https://leetcode.com/tag/string/