For the “Words Concatenation (hard)” problem (Problem Challenge 4 of the Sliding Window pattern), the solution provided in the course is not the optimal solution, at least in terms of time complexity.

Could the course be updated to include the optimal solution, or at the very least indicate that the solution provided is not optimal? This would go a long way into helping users trust the course and its content. Thanks!

A faster solution can be found, for example, in Leetcode (Problem 30. Substring with Concatenation of All Words). The faster solution would be Approach 2 in the solution tab for the problem.

Course: Grokking the Coding Interview: Patterns for Coding Questions - Learn Interactively

Lesson: Solution Review: Problem Challenge 4 - Grokking the Coding Interview: Patterns for Coding Questions