CircularTour.java

package Queue;

public class CircularTour {

    static int printTour(petrolPump[] arr, int n) {
        int start = 0;
        int end = 1;
        int curr_petrol = arr[start].petrol - arr[start].distance;

        // If current amount of petrol in truck becomes less than 0, then remove the starting petrol pump from tour
        while (end != start || curr_petrol < 0) {
            while (curr_petrol < 0 && start != end) {

                curr_petrol -= arr[start].petrol - arr[start].distance;
                start = (start + 1) % n;
                if (start == 0) return -1;
            }
            curr_petrol += arr[end].petrol - arr[end].distance;
            end = (end + 1) % n;
        }
        return start;
    }

    public static void main(String[] args) {

        petrolPump[] arr = {new petrolPump(6, 4),
                new petrolPump(3, 6),
                new petrolPump(7, 3)};

        int start = printTour(arr, arr.length);
        System.out.println(start == -1 ? "No Solution" : "Start = " + start);
    }

    static class petrolPump {
        int petrol;
        int distance;

        public petrolPump(int petrol, int distance) {
            this.petrol = petrol;
            this.distance = distance;
        }
    }
}