Refocus CSP guide to 300-point scope with practical algorithm branches and 2024–2025 exam practice

[Copilot]

The issue asked to reduce the guide’s scope to CSP 300-level essentials, avoid overly advanced algorithm coverage, add practical sub-branches under major topics (especially for two pointers), and include recent 2024–2025 exam practice.
This update restructures the README accordingly with a tighter, exam-oriented progression.

• Scope narrowed to CSP300 essentials

  • Replaced generic/advanced framing with a T1–T4 strategy focused on securing T1–T3.
  • Kept only high-frequency patterns needed for 300-point preparation.

• Major algorithms split into practical sub-branches

  • Added concise “big topic → small branch” breakdowns.
  • Explicitly split two pointers into:
    • Sliding window
    • Left-right pointers
    • Fast-slow pointers
  • Simplified DP to common-use patterns (linear DP, 0/1 knapsack, basic state transitions).

• Recent exam practice added (2024–2025)

  • Added a dedicated section listing 2024 and 2025 sessions for T1–T3 practice.
  • Included a short, repeatable practice loop for timed attempts and targeted replay.

• Concrete template included

  • Added a minimal 0/1 knapsack C++ template aligned with CSP300-level usage:

for (int i = 1; i <= n; i++) {
    for (int j = W; j >= w[i]; j--) {
        dp[j] = max(dp[j], dp[j - w[i]] + v[i]);
    }
}

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