What is the difference that you see between these sorts of algorithm puzzle contests?
Is there some reason that people who are good at one contest would be bad at another, similar contest?
Leetcode works like this. Company A is asking these 100 questions with this frequency; let me solve these questions so that when I encounter these in the interview I can solve them then. The whole premise of Leetcode is on giving a question bank to what is already being asked. The aim is to clear the base bar a company has set.
There are some people who basically just do competitive programming to be good for interviews, but they don't get very far - not even to div 1. They reach whatever bar is necessary to clear an interview and quit immediately. The people who seriously compete to go for ICPC World Finals or to get far in CodeJam, they aren't really concerned with interviews.
The problem is LeetCode is SO BORING for anyone ever tried competitive programming so people usually won't do it at all.