ZOPSMART ON-CAMUS ROUND DETAILS

I recently gave the online assessment of zop smart. CTC 10 LPA.
These questions were asked
a.) Trapping Rain Water (with some modification)
(Basiclally given some chars first convert to ascii then solve)
https://leetcode.com/problems/trapping-rain-water/description/
b.) I didn't find this problem anywhere. Basically the problem was
"Given a string say "RAGHAV". Now convert "R" to ascii, "A" to ascii and so on
"R" in ASCII=82. So nearest square =81 (which is of "Q").
Similarly i need to find char representation of nearest square of each number. (I tried pre computing all the sqaures till 400 then solving. but time finished)