LeetCode Priority Queue schedule template

class Solution {

    public int[] assignTasks(int[] servers, int[] tasks) {
        // <weight, index>
        PriorityQueue<int[]> available = new PriorityQueue<>((a, b) -> (a[0] == b[0] ? a[1] - b[1] : a[0] - b[0]));
        // <time, weight, index>
        PriorityQueue<int[]> using = new PriorityQueue<>((a, b) -> {
            if (a[0] == b[0]) {
                if (a[1] == b[1]) {
                    return a[2] - b[2];
                } 
                return a[1] - b[1];
            }
            return a[0] - b[0];
        });
        int[] res = new int[tasks.length];
        Queue<Integer> q = new LinkedList<>();
        
        for (int i = 0; i < servers.length; i++) {
            available.offer(new int[]{servers[i], i});
        }
        
        for (int i = 0; i < tasks.length; i++) {
            q.offer(i);
            // put using to available
            while (!using.isEmpty() && using.peek()[0] <= i) {
                int[] toAvailable = using.poll();
                available.offer(new int[]{toAvailable[1], toAvailable[2]});
            }
            // assign tasks from available
            while (!q.isEmpty() && !available.isEmpty()) {
                int[] server = available.poll();
                int t = q.poll();
                res[t] = server[1];
                using.offer(new int[] {tasks[t] + i, server[0], server[1]});
            }
        }
        
        // tasks in the queue waiting for servers in using 
        while (!q.isEmpty()) {
            int[] server = using.poll();
            int task = q.poll();
            res[task] = server[2];
            using.offer(new int[] {server[0] + tasks[task], server[1], server[2]});
        }
        return res;
    }
}