2022.7.2-----leetcode. eight hundred and seventy-one

  public int minRefuelStops(int target, int startFuel, int[][] stations) {
        // The amount of fuel you can choose for a journey 
        PriorityQueue<Integer> pq = new PriorityQueue<Integer>((a, b) -> b - a);
        int ans = 0,end = startFuel;// The maximum distance of a journey 
        int n = stations.length;
        for (int i = 0; i < n; i++) {
            if(end>=target) return ans;// If you can reach the end of a journey, you will return 
            // After reaching the maximum distance , Select the maximum fuel volume , Until it's enough to reach the next station , Start the next journey 
            if(stations[i][0]>end){
               while(!pq.isEmpty()) {
                end+=pq.poll();
                ans++;
                if(end>=stations[i][0]) break;
               }
               if(end<stations[i][0]) return -1;// Unable to reach the next site   
            } 
            pq.add(stations[i][1]);// Add the amount of fuel that can reach the station 
        }
        // After passing all sites , Judge whether you can reach the end 
        if(end<target){
            while(!pq.isEmpty()) {
                end+=pq.poll();
                ans++;
                if(end>=target) return ans;
            }
            return -1;
        }
        return ans;
    }