https://codeforces.me/contest/1985/problem/H1. For this problem when I am running the same code on VS code it is coming correct but when I am submitting it is showing garbage value. 271078629

How to approach problems for DP? and as a beginner should I start approaching the question in tabulation method or in recursive method and then change it to the tabulation method ?

https://codeforces.me/contest/1983/problem/D

In this problem. Count inversion concept comes into play but why ?? What is the exact intuition behind it? Like why only count inversion. and what are the other type of problems where this concept is used.

I cant understand why https://codeforces.me/contest/1987/submission/268352950 is not giving TLE but this is https://codeforces.me/contest/1987/submission/268340248. Both have same approach for the same question.