https://leetcode.com/problems/minimum-number-of-refueling-stops/

871.java

class Solution {
    public int minRefuelStops(int target, int startFuel, int[][] stations) {
        int p = 0; // position
        int i = 0; // index of first unreachable station
        var q = new PriorityQueue<Integer>(stations.length/2 + 1, Collections.reverseOrder());
        q.add(startFuel);

        int refills = -1; // we count initial fuel as a filling too, so initialize to -1
        while (p < target) {
            if (q.isEmpty()) {
                return -1;
            }
            p += q.poll();
            refills++;
            while (i < stations.length && stations[i][0] <= p) {
                q.add(stations[i][1]);
                i++;
            }
        }
        return refills;
    }
}