System Design — Ring Buffer (Bounded Log)

A fixed-size circular buffer: the structure behind log tails, audio buffers and metric
windows. Writing to a full buffer overwrites the oldest value.

solve(args, ops) builds new RingBuffer(capacity) — args = [capacity] — and replays
ops:

• write(value) — append value; if the buffer is full, drop the oldest value first.

Returns nothing.

• read() — remove and return the oldest value, or null if the buffer is empty.
• snapshot() — return all values as an array, oldest first, without removing them.
• size() — the number of values currently stored.

All operations except snapshot must be O(1): allocate the array once and move a start
index and a size counter around it with modulo arithmetic — no shift().

Example (capacity = 3)

write(1) write(2) write(3) write(4)  snapshot() → [2,3,4]     // 1 was overwritten
read() → 2