Hi everyone, I just created a new account on Codeforces to practice competitive programming. I am currently a Newbie I am comfortable with basic programming syntax, but I want to improve my problem-solving skills systematically. I can usually solve problems A and B in Div. 3 or Div. 4 contests, but I often get stuck on problem C or when a problem requires specific algorithmic thinking. I would appreciate any advice on the following questions:

1. What core algorithms or mathematical topics should a Newbie master first to consistently solve Div. 3/Div. 4 C problems?What is the most effective way to practice?

2. Should I solve problems by specific tags (like greedy or math) or just pick random problems from the problemset within a specific rating range (e.g., 1100–1200)?

3. Are there any specific training sheets, ladders, or groups you recommend for someone at my level? Thank you for your time and guidance!