Implement Queue using Stacks
Implement a FIFO queue using only two stacks. Think about: How can two stacks simulate queue behavior? Hint: Use one stack for push, another for pop/peek. Example: push(1), push(2) peek() → 1 (front of queue) pop() → 1 peek() → 2
Implement Queue using Stacks rewards disciplined state tracking more than raw coding speed. It's a great warm-up that builds stack invariants without a ton of moving parts. Keep the stack invariant explicit; if it breaks, everything downstream breaks too.
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