I created a video on 3 different techniques to count distinct subsequences of a string.

• $$$O(N^3)$$$ Lexicographic Minimal DP on Indices
• $$$O(N^2)$$$ Lexicographic Maximal Character DP
• $$$O(N^2)$$$ Lexicographic Maximal PIE DP

Video https://youtu.be/DZ8sVn4W6IQ

Practice Problem H. Subsequences (hard version)