Circular Tour

#include <bits/stdc++.h>
using namespace std;

class petrolPump
{
	public:
	int petrol;
	int distance;
};

int printTour(petrolPump arr[], int n)
{
	int start = 0;
	int end = 1;

	int curr_petrol = arr[start].petrol - arr[start].distance;
	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;
}
int main()
{
	petrolPump arr[] = {{6, 4}, {3, 6}, {7, 3}};

	int n = sizeof(arr)/sizeof(arr[0]);
	int start = printTour(arr, n);

	(start == -1)? cout<<"No solution": cout<<"Start = "<<start;

	return 0;
}


// Time COmplexity  O(N)
// space Complexity O(1)