SQRDSUB help

Can anyone explain why my code gives errors on every fking testcase to the SQRDSUB problem from this month’s long challenge?
My Submission

My main solution logic is in void solve(int tc) function

Well, so as an explanation for the code, I am computing using DP the number of substrings (contiguous subsequences) ending at every index and having remainder modulo 4 as 0,1,2 or 3 in the ‘b’ vector.
And at the end, I sum over all such indices and don’t take the substrings having values as 2 mod 4