Method smallestChair

NumberOfSmallestUnoccupiedChair.java:3–35

(int[][] times, int targetFriend)

class Solution {
    public int smallestChair(int[][] times, int targetFriend) {
        int targetArrival = times[targetFriend][0]; //[a,d]
        Arrays.sort(times, new Comparator<int[]>(){
            public int compare(int a[], int b[]){
                return a[0] - b[0];
            }
        });
        //[lt,chairNo]
        PriorityQueue<int[]> occupied = new PriorityQueue<>(new Comparator<int[]>(){
            public int compare(int a[], int b[]){
                return a[0] - b[0];
            }
        });
        PriorityQueue<Integer> available = new PriorityQueue<>();
        int chairNo=0;
        for(int time[] : times){
            int arrTime = time[0];
            int leavingTime = time[1];
            while(!occupied.isEmpty() && occupied.peek()[0] <= arrTime){
                available.offer(occupied.poll()[1]);
            }
            int currentChairNo;
            if(available.isEmpty()){
                currentChairNo = chairNo;
                chairNo++;
            }else{
                currentChairNo = available.poll();
            }
            if(targetArrival == arrTime) return currentChairNo;
            occupied.offer(new int[]{leavingTime, currentChairNo});
        }
        return -1;
    }
}