A hybrid logical clock combines a wall-clock component with a logical counter. The pair preserves causality even when the local physical clock stalls or moves backward.
Design a HybridLogicalClock class:
HybridLogicalClock() starts at timestamp [0, 0].int[] local(int physicalTime) records a local event and returns the updated timestamp.int[] receive(int physicalTime, int remoteWall, int remoteLogical) records receipt of a remote timestamp and returns the updated timestamp.
For a local event:
- If
physicalTime is greater than the stored wall component, set the wall component to physicalTime and reset the logical component to 0. - Otherwise, keep the stored wall component and increment the logical component.
For a received event, let nextWall be the maximum of physicalTime, the stored wall component, and remoteWall. Compute the new logical component as follows:
- If both the stored wall and
remoteWall equal nextWall, use max(storedLogical, remoteLogical) + 1. - Otherwise, if only the stored wall equals
nextWall, use storedLogical + 1. - Otherwise, if only
remoteWall equals nextWall, use remoteLogical + 1. - Otherwise the physical clock is strictly greatest, so use
0.
Store and return [nextWall, nextLogical].
Example 1:
Input:
Output:
Explanation: The first event follows physical time. The second event uses the logical counter because physical time is unchanged. The received timestamp then advances beyond logical values 1 and 4.
Example 2:
Input:
Output:
Explanation: Physical time 50 is strictly greater than both wall components, so the logical component resets to 0.
Constraints
0 <= physicalTime, remoteWall <= 10^90 <= remoteLogical <= 10^9- Physical times supplied to one clock may stay unchanged or move backward.
- Every returned component fits in a signed 32-bit integer.
- At most
10^5 method calls are made per clock.
Advance a Hybrid Logical Clockhard