Patterns

Track multiple dp states (e.g., holding/not-holding stock); transition between states each step

When to useStock buy/sell variants with cooldown, transaction limits, paint house

DECLARE

one variable per state (e.g., hold, cash) or dp[i][state]

—

BASE CASES

init each state's value at step 0 (e.g., hold = -prices[0], cash = 0)

—

BUILD

for each step from 1 onward

—

[RECURRENCE]

compute next state values from current; update

  if (price - minSoFar > best) best = price - minSoFar;

  if (prices[i] > prices[i - 1]) profit += prices[i] - prices[i - 1];

RETURN

return the desired final state

return best;

return profit;