ChargePoint Team Leader interview questions

I had initial first round of discussion, where I was asked to code for one problem. Then I was given one problem from LeetCode#289, to solve & submit the solution. Second round of discussion was about the solution that how can I improve the solution. Interviewer wanted me to see the pattern in the data to think about Sparse Matrix, which I don't see till date & don't see any applicability of Sparse matrix here.. If you have nothing to do & have enough free time then try for this. And Glassdoor is useless as usual.