Dynamic Programming, Greedy, Intervals

Learn — for DP, name the state and the transition out loud before writing anything; if you cannot say them, you are not ready to type. Greedy needs a proof — if you cannot argue it, it is DP. For intervals, whether you sort by start or by end is the entire decision.

Do — problems 77–100.

Check — you can give the counterexample where greedy coin change fails (coins [1,3,4], amount 6); you can say why Non-overlapping Intervals sorts by end and Merge Intervals sorts by start; you can state your Kadane invariant.

Ship — repo complete, all 100 problems.

Then stop adding problems. Problem 101 teaches you less than re-solving number 47 does.