Thanks a lot! I would never think about it.

Hi! Why does this submission 159869794 get AC, but this 159757251 — WA?

But some people see. Maybe it's personal, individual?

"they can keep up the grind" — that's the main problem. Newbies solve hundreds of problems and don't get any result, because they are grinding. They skip hard problems, trying to maximise a number of solved problems, not their skills.

There is actually a good post about it: this one

Use an ArrayList of Integers and Collections.sort(), it's always O(nlogn). Arrays.sort() is O(n^2), although docs say it is O(nlogn).

Thanks.

What was the key idea for A?

Maybe, it's not that useful for competitive programming, but it allows to write code in a modern style. Just try to write a solution in a Java 7 style and you'll feel the difference.

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