What is the optimal solution for LeetCode 309 cooldown stock problem?

O(n) DP with buy/sell/cooldown states, O(1) space via variable mutation. Max profit handles multiple trades post-1-day wait.

Why use three states in LeetCode 309 DP?

Captures post-buy, post-sell, post-cooldown maxima—prevents invalid buy-after-sell jumps.

309 adds cooldown state; 122 skips it for simpler buy/sell toggle.

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LeetCode 309? Over 1.2 million attempts, 38% success rate. This DP state machine turns cooldown chaos into max-profit gold.

theAIcatchup Apr 09, 2026 4 min read

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Originally reported by Dev.to