[Swift]LeetCode1232.缀点成线 | Check If It Is a Straight Line

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You are given an array coordinates, coordinates[i] = [x, y], where [x, y] represents the coordinate of a point. Check if these points make a straight line in the XY plane.

Example 1:

 

Input: coordinates = [[1,2],[2,3],[3,4],[4,5],[5,6],[6,7]]
Output: true
Example 2:

 

Input: coordinates = [[1,1],[2,2],[3,4],[4,5],[5,6],[7,7]]
Output: false

Constraints:

2 <= coordinates.length <= 1000
coordinates[i].length == 2
-10^4 <= coordinates[i][0], coordinates[i][1] <= 10^4
coordinates contains no duplicate point.

---

在一个 XY 坐标系中有一些点，我们用数组 coordinates 来分别记录它们的坐标，其中 coordinates[i] = [x, y] 表示横坐标为 x、纵坐标为 y 的点。

请你来判断，这些点是否在该坐标系中属于同一条直线上，是则返回 <font color="#c7254e" face="Menlo, Monaco, Consolas, Courier New, monospace">true</font>，否则请返回 <font color="#c7254e" face="Menlo, Monaco, Consolas, Courier New, monospace">false</font>。

示例 1：

输入：coordinates = [[1,2],[2,3],[3,4],[4,5],[5,6],[6,7]]
输出：true
示例 2：

输入：coordinates = [[1,1],[2,2],[3,4],[4,5],[5,6],[7,7]]
输出：false

提示：

2 <= coordinates.length <= 1000
coordinates[i].length == 2
-10^4 <= coordinates[i][0], coordinates[i][1] <= 10^4
coordinates 中不含重复的点

---

40ms

class Solution {
    func checkStraightLine(_ coordinates: [[Int]]) -> Bool {
    let cur = coordinates[0]
    let next = coordinates[1]
    
    let num = next[1] - cur[1]
    let denom = next[0]-cur[0]
    
    let slope = Double(num)/Double(denom)
    
    for i in 1..<coordinates.count-1{
        let cur = coordinates[i]
        let next = coordinates[i+1]
        
        let curNum = next[1] - cur[1]
        let curDenom = next[0]-cur[0]
        let cSlope = Double(curNum)/Double(curDenom)
        
        if( cSlope != slope ){
            return false
        }
    }
     return true
    }
}

---

44ms

class Solution {
    func checkStraightLine(_ coordinates: [[Int]]) -> Bool {
        let dx = coordinates[1][0] - coordinates[0][0]
        let dy = coordinates[1][1] - coordinates[0][1]
        for i in 2..<coordinates.count {
            let dx1 = coordinates[i][0] - coordinates[0][0]
            let dy1 = coordinates[i][1] - coordinates[0][1]
            if dx == 0 && dx1 != 0 {
                return false
            }
            if dy == 0 && dy1 != 0 {
                return false
            }
            if dy == 0 && dy1 == 0 {
                continue
            }
            let dx2 = Double(dx) * Double(dy1) / Double(dy)
            if Double(dx1) != dx2 {
                return false
            }
        }
        return true
    }
}

---

48ms

class Solution {
    func getGradient(x2: Int, x1: Int, y2: Int, y1: Int) -> Double {
        return Double(y2 - y1) / Double(x2 - x1)
    }
    
    func checkStraightLine(_ coordinates: [[Int]]) -> Bool {
        var coordinates = coordinates
        if coordinates.count < 2 {
            return false
        }
        
        var first = coordinates.removeFirst()
        var gradient: Double = 0.0
        
        for point in coordinates {
            let currentGradient = getGradient(x2: point[0], x1: first[0], y2: point[1], y1: first[1])
            if gradient == 0.0 {
                gradient = currentGradient
            }
            if gradient != currentGradient {
                return false
            }
        }
        return true
    }
}