State Machine DP

Model the problem as explicit states (holding stock / not holding / in cooldown, for example) with transitions each step; dp tracks the best value per state.

Sub-patterns

• A — Buy/Sell Stock Family. Holding vs. not holding, with cooldown and transaction-fee variants.
• B — General Finite-State Transition DP. The same explicit-states-and-transitions idea applied beyond stock problems.

Practice set (6)

• Easy — Best Time to Buy and Sell Stock
• Medium — Best Time to Buy and Sell Stock II, Best Time to Buy and Sell Stock with Cooldown, Best Time to Buy and Sell Stock with Transaction Fee
• Hard — Best Time to Buy and Sell Stock III, Best Time to Buy and Sell Stock IV