LeetCode 1184. Distance Between Bus Stops

Description

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

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.

Constraints:

  • 1 <= n <= 10^4
  • distance.length == n
  • 0 <= start, destination < n
  • 0 <= distance[i] <= 10^4

Explanation

Two scenarios, one is: start < destination, the other is: start > destination. In both scenarios, we check whether the minimum distance is either clockwise or counterclockwise.

Python Solution

class Solution:
    def distanceBetweenBusStops(self, distance: List[int], start: int, destination: int) -> int:
                
        if start < destination:        
            min_distance = min(sum(distance[start:destination]), (sum(distance[destination:]) + sum(distance[:start])))
        else:
            min_distance = min(sum(distance[destination:start]), (sum(distance[start:]) + sum(distance[:destination])))
            
        
        return min_distance
  • Time Complexity: O(N).
  • Space Complexity: O(1).

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