Coding stack
Valid Parentheses + Min Stack
LC 20, 155. Dual-stack min. Speak the invariant: top of min stack is current min.
LC 20, 155. Dual-stack min. Speak the invariant: top of min stack is current min.
LC 739. Next-greater template. Store indices, not values.
LC 84. Sentinel zeros. Narrate why each bar pops when it does.
Liveness vs readiness, slow-start, and cascading failure from bad probes.