Practice/Apple/Job Scheduling Algorithms Implementation

Job Scheduling Algorithms Implementation

CodingMust

Problem

You are building a process scheduler for an operating system that needs to support multiple scheduling strategies. Given a list of processes and a scheduling strategy, determine the execution order and calculate timing metrics for each process.

Each process is represented as [arrival_time, burst_time, priority] where:

• arrival_time: The time when the process arrives in the ready queue
• burst_time: The total execution time needed for the process
• priority: Priority level (higher numbers indicate higher priority)

Your scheduler must support two strategies:

• FCFS (First Come First Serve): Processes are executed in the order they arrive
• PRIORITY: Processes are executed based on priority (higher priority first). If priorities are equal, use arrival time as a tiebreaker

Return a list of [arrival_time, completion_time, waiting_time] for each process in the original input order.

Requirements

1. Implement both FCFS and priority-based scheduling algorithms
2. Calculate completion time for each process (when it finishes execution)
3. Calculate waiting time for each process (time spent in queue before starting execution)
4. For FCFS, maintain strict arrival order
5. For PRIORITY, execute highest priority processes first
6. If a process arrives after the CPU is idle, start it immediately
7. Return results in the same order as input processes

Constraints

• 1 ≤ processes.length ≤ 1000
• 0 ≤ arrival_time ≤ 10^6
• 1 ≤ burst_time ≤ 1000
• 1 ≤ priority ≤ 10
• All time values are non-negative integers
• Strategy will be either "FCFS" or "PRIORITY"

Examples

Example 1:

` Input: processes = [[1, 3, 2], [2, 5, 1], [4, 6, 3]], strategy = "FCFS" Output: [[1, 4, 0], [2, 9, 2], [4, 15, 5]] Explanation:

• Process 0 arrives at time 1, starts immediately, completes at time 4 (1+3), waiting time = 0
• Process 1 arrives at time 2, waits until time 4, completes at time 9 (4+5), waiting time = 2
• Process 2 arrives at time 4, waits until time 9, completes at time 15 (9+6), waiting time = 5 `

Example 2:

` Input: processes = [[0, 4, 2], [1, 3, 1], [2, 2, 3]], strategy = "PRIORITY" Output: [[0, 6, 2], [1, 9, 5], [2, 4, 0]] Explanation:

• Process 2 has highest priority (3), arrives at time 2, executes first after process 0 starts
• Process 0 has priority 2, starts at time 0, completes at time 4
• Process 2 executes from time 4 to 6
• Process 1 has lowest priority (1), executes last from time 6 to 9 `

Example 3:

Input: processes = [[0, 5, 1]], strategy = "FCFS" Output: [[0, 5, 0]] Explanation: Single process starts immediately at time 0 and completes at time 5