Cannot state enough that LeetCode is your friend here. LeetCode Premium is definitely worth it if you can afford it.

Books

• Cracking the Code Interview by Gayle Laakmann McDowell

Trees

• DFS
  • GeeksForGeeks
• isTree
  • GeeksForGeeks
• Kth Smallest Element in BST
  • LeetCode

Strings

• Leetcode Pattern 2 - Sliding windows for strings
• Leetcode: Decode string with multipliers
• Longest common prefix

Arrays

• Shuffling
  • Wikipedia
  • i-programmer

Dynamic programming

• Follow these steps to solve any Dynamic Programming interview problem
• Change the signs: how to use dynamic programming to solve a competitive programming question
• ITNEXT Medium: DP vs DC

Sorting

• Count inversions with merge sort

Misc

• Leetcode: LRU
• Skyline Problem
  • Leetcode
  • Brian Gordon