#283 Fixed-Size Log Buffer

An embedded analytics script must not grow its memory, so it stores pending log entries in a circular queue of fixed size capacity. Write a class LogBuffer:

• new LogBuffer(capacity) creates an empty buffer.
• enqueue(entry) adds an entry at the back and returns true, or returns false if the buffer is full.
• dequeue() removes the oldest entry and returns true, or returns false if the buffer is empty.
• front() and rear() return the oldest and newest entries, or -1 if empty.
• isEmpty() and isFull() return booleans.

Use a fixed array of size capacity with wrap-around indexes; don't grow or shift an array.

Each example lists the calls in order, then each call's arguments. The first call creates the object with new LogBuffer(…); the output lists what each call returns (null for the constructor and for methods that return nothing).

Input: ["LogBuffer","enqueue","enqueue","enqueue","enqueue","rear","isFull","dequeue","enqueue","rear","front"]
[[3],[1],[2],[3],[4],[],[],[],[4],[],[]]
Output: [null,true,true,true,false,3,true,true,true,4,2]

Input: ["LogBuffer","front","rear","dequeue","isEmpty"]
[[2],[],[],[],[]]
Output: [null,-1,-1,false,true]

Constraints

• 1 <= capacity <= 1000
• 0 <= entry <= 1000
• At most 3000 calls.