Can someone help me by giving me feedback on how to improve my rating? I am feeling stuck, I am unable to improve myslef, which results in making me stuck in Grey. This is also making me a bit frustrated.

What I do for practice -> I am solving this Sheet currently. I am currently practicing 1000-110 rated problems. I have solved the 800-900 rated problems from this. What I do while solving a problem is --> I first try to implement the intuition that first comes up, then I am either able to implement it or while implementing I realize my intuition is not correct, and after this, I just get stuck on one intuition, I am unable to think of any other intuition, I still try to come with an intuition which is very similar to I previously thought of. if I am unable to solve a problem after thinking for 30-60 mins, I look at the solution.

There are many times, when I am unable to think of any intuition and then I right away look at the solution within 20-30 mins

Like in the last Contest 969, I was unable to solve any problem, I started solving A and got frustrated when I thought my logic of finding coprime triplet, was giving WA. Then after feeling disappointed, I was unable to solve B, even though solving B required just a bit of observation

So here is the problem I am facing, for the problem --> 1827A - Counting Orders, I am getting AC when using a solution using arrays, and getting a TLE when using ArrayList.

Here are the two solutions: using Array --> 278615778 using ArrayList --> 278616942

So tell me whether I should use ArrayList or Arrays for solving problems because this is not the only problem where I have faced this issue, there were others also.

Can anyone who has experience using Java tell me whether I should use ArrayList or Arrays?