[Swift]LeetCode1184. 公交站间的距离 | Distance Between Bus Stops

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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

---

环形公交路线上有 n 个站，按次序从 0 到 n - 1 进行编号。我们已知每一对相邻公交站之间的距离，distance[i] 表示编号为 i 的车站和编号为 (i + 1) % n 的车站之间的距离。

环线上的公交车都可以按顺时针和逆时针的方向行驶。

返回乘客从出发点 start 到目的地 destination 之间的最短距离。

 

示例 1：

输入：distance = [1,2,3,4], start = 0, destination = 1
输出：1
解释：公交站 0 和 1 之间的距离是 1 或 9，最小值是 1。

 

示例 2：

输入：distance = [1,2,3,4], start = 0, destination = 2
输出：3
解释：公交站 0 和 2 之间的距离是 3 或 7，最小值是 3。

 

示例 3：

输入：distance = [1,2,3,4], start = 0, destination = 3
输出：4
解释：公交站 0 和 3 之间的距离是 6 或 4，最小值是 4。

 

提示：

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

---

20ms

class Solution {
    func distanceBetweenBusStops(_ distance: [Int], _ start: Int, _ destination: Int) -> Int {
        var path = [0, 0]
        
        let lo = min(start, destination)
        let hi = max(start, destination)

        
        for i in 0 ..< lo {
            path[0] += distance[i]
        }
        for i in lo ..< hi {
            path[1] += distance[i]
        }
        for i in hi ..< distance.count {
            path[0] += distance[i]
        }
        
        return path[0] < path[1] ? path[0] : path[1]
    }
}

---

Runtime: 24 ms

Memory Usage: 21.3 MB

class Solution {
    func distanceBetweenBusStops(_ distance: [Int], _ start: Int, _ destination: Int) -> Int {
        var S:Int = 0
        var T:Int = 0
        var sum:Int = 0
        for i in 0..<distance.count
        {
            if i == start {S=sum}
            if i == destination {T=sum}
            sum += distance[i]
        }
        return min(abs(T-S),sum-abs(T-S))
    }
}

---

24ms

 

class Solution {
    func distanceBetweenBusStops(_ distance: [Int], _ start: Int, _ destination: Int) -> Int {
        var pathA = 0
        var pathB = 0
        
        let lo = start < destination ? start : destination
        let hi = start > destination ? start : destination

        for i in 0 ..< lo {
            pathA += distance[i]
        }
        for i in lo ..< hi {
            pathB += distance[i]
        }
        for i in hi ..< distance.count {
            pathA += distance[i]
        }
        
        return pathA < pathB ? pathA : pathB
    }
}

---

28ms

class Solution {
    func distanceBetweenBusStops(_ distance: [Int], _ start: Int, _ destination: Int) -> Int {
        var path = [0, 0]
        
        let lo = min(start, destination)
        let hi = max(start, destination)

        
        for i in 0 ..< lo {
            path[0] += distance[i]
        }
        for i in lo ..< hi {
            path[1] += distance[i]
        }
        for i in hi ..< distance.count {
            path[0] += distance[i]
        }
        
        return path[0] < path[1] ? path[0] : path[1]
    }
}

---

32ms

class Solution {
    func distanceBetweenBusStops(_ distance: [Int], _ start: Int, _ destination: Int) -> Int {
        let a = min(start, destination)
    let b = max(start, destination)
    let sumDistance = distance.reduce(0) { result, num in result+num }
    var sum = 0
    for i in a..<b {
        sum += distance[i]
    }
    return min(sum, sumDistance-sum)
    }
}