In Codeforces Round 433 Div 2, I have seen a solution of problem E.

Since, the value of n was 200000. So it was not possible to solve the problem by declaring a n*n(200000*200000) array.

But, In that solution a solver has used a vector efficiently instead of two dimensional array. I have tried but couldn't got this.

Can anyone please help me on this?

Thanks in advance.