General Question

What’s the complexity of this solution?

Problem: Problem - B2 - Codeforces

I can see O(n)
but gives TLE on test case 18

Your time comp is O(t*(n+k+d)).
So ,it is getting TLE.
For tc 18 t=1000 k=1000000

How can I improve on this, editorial says to use two pointers technique but that won’t get any better i guess ? complexity is actually O(t*(2n)) as k+d =n.

Take set and insert values till d. Now add 1 element and remove the last element and check size of set. You have to find min size.
Time comp is O(tnlogn)

It is guaranteed that the sum of the values ​​of n for all test cases in the input does not exceed 2⋅10^5.

So, this will be fine