Distance between bus stops

Time: O(N); Space: O(1); easy

A bus has N stops numbered from 0 to N - 1 that form a circle. We know the distance between all pairs of neighboring stops where distance[i] is the distance between the stops number i and (i + 1) % N. The bus goes along both directions i.e. clockwise and counterclockwise.

Return the shortest distance between the given start and destination stops.

Example 1:

Input: distance = [1,2,3,4], start = 0, destination = 1

Output: 1

Explanation:

• Distance between 0 and 1 is 1 or 9, minimum is 1.

Example 2:

Input: distance = [1,2,3,4], start = 0, destination = 2

Output: 3

Explanation:

• Distance between 0 and 2 is 3 or 7, minimum is 3.

Example 3:

Input: distance = [1,2,3,4], start = 0, destination = 3

Output: 4

Explanation:

• Distance between 0 and 3 is 6 or 4, minimum is 4.

Notes:

• 1 <= n <= 10^4

• len(distance) == n

• 0 start, destination < n

• 0 distance[i] <= 10^4

import itertools

class Solution1(object):
    def distanceBetweenBusStops(self, distance, start, destination):
        """
        :type distance: List[int]
        :type start: int
        :type destination: int
        :rtype: int
        """
        if start > destination:
            start, destination = destination, start
        s_to_d = sum(itertools.islice(distance, start, destination))
        d_to_s = sum(itertools.islice(distance, 0, start)) + \
                 sum(itertools.islice(distance, destination, len(distance)))
        return min(s_to_d, d_to_s)

s = Solution1()
distance = [1,2,3,4]
start = 0
destination = 1
assert s.distanceBetweenBusStops(distance, start, destination) == 1
distance = [1,2,3,4]
start = 0
destination = 2
assert s.distanceBetweenBusStops(distance, start, destination) == 3
distance = [1,2,3,4]
start = 0
destination = 3
assert s.distanceBetweenBusStops(distance, start, destination) == 4

See also:

https://leetcode.com/problems/distance-between-bus-stops