Greedy implementation of Max Refills Problem

min_refills.py

def min_refills(stations, full_tank_limit):
    """
    Find min refills for gas tank in a trip between point A and B

    Args:
    stations (array): possible gas stations to refill including start(A) and end(B).
    full_tank_limit (int): gas tank maximum limit.

    Returns:
    (int) number of refills needed to make the trip between A -> B

    Running time: O(n)
    current_ref ranges between 0 and n - 1 so the outer and inner loop 
    does not actually multiply (n * n = O(n^2)).
    """
    current_refill, num_refills = 0, 0
    n = len(stations) - 1
    while current_refill < n:
        last_refill = current_refill
        while (
            current_refill < n
            and stations[current_refill + 1] - stations[last_refill] <= full_tank_limit
        ):
            current_refill += 1
        if current_refill == last_refill:
            return -1
        if current_refill < n:
            num_refills += 1
    return num_refills

# Example
stations = [0, 200, 375, 550, 750, 950]
max_lim = 400

min_refill(stations, max_lim) # --> 2