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package g0801_0900.s0871_minimum_number_of_refueling_stops;

// #Hard #Array #Dynamic_Programming #Greedy #Heap_Priority_Queue
// #2022_03_28_Time_3_ms_(88.52%)_Space_48.8_MB_(60.04%)

import java.util.PriorityQueue;

public class Solution {
    public int minRefuelStops(int target, int startFuel, int[][] stations) {
        if (startFuel >= target) {
            return 0;
        } else if (stations == null || stations.length == 0) {
            return -1;
        }
        PriorityQueue pq = new PriorityQueue<>((a, b) -> b[1] - a[1]);
        int start = 0;
        int end = stations.length;
        int currentFuel = startFuel;
        int stops = 0;
        while (currentFuel < target) {
            while (start < end && currentFuel >= stations[start][0]) {
                pq.add(stations[start++]);
            }
            if (pq.isEmpty()) {
                return -1;
            }
            int[] current = pq.poll();
            currentFuel += current[1];
            stops++;
        }
        return stops;
    }
}