[Swift]LeetCode1232.缀点成线|CheckIfItIsaStraightLine

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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

 1 class Solution {
 2     func checkStraightLine(_ coordinates: [[Int]]) -> Bool {
 3     let cur = coordinates[0]
 4     let next = coordinates[1]
 5     
 6     let num = next[1] - cur[1]
 7     let denom = next[0]-cur[0]
 8     
 9     let slope = Double(num)/Double(denom)
10     
11     for i in 1..<coordinates.count-1{
12         let cur = coordinates[i]
13         let next = coordinates[i+1]
14         
15         let curNum = next[1] - cur[1]
16         let curDenom = next[0]-cur[0]
17         let cSlope = Double(curNum)/Double(curDenom)
18         
19         if( cSlope != slope ){
20             return false
21         }
22     }
23      return true
24     }
25 }

44ms

 1 class Solution {
 2     func checkStraightLine(_ coordinates: [[Int]]) -> Bool {
 3         let dx = coordinates[1][0] - coordinates[0][0]
 4         let dy = coordinates[1][1] - coordinates[0][1]
 5         for i in 2..<coordinates.count {
 6             let dx1 = coordinates[i][0] - coordinates[0][0]
 7             let dy1 = coordinates[i][1] - coordinates[0][1]
 8             if dx == 0 && dx1 != 0 {
 9                 return false
10             }
11             if dy == 0 && dy1 != 0 {
12                 return false
13             }
14             if dy == 0 && dy1 == 0 {
15                 continue
16             }
17             let dx2 = Double(dx) * Double(dy1) / Double(dy)
18             if Double(dx1) != dx2 {
19                 return false
20             }
21         }
22         return true
23     }
24 }

48ms

 1 class Solution {
 2     func getGradient(x2: Int, x1: Int, y2: Int, y1: Int) -> Double {
 3         return Double(y2 - y1) / Double(x2 - x1)
 4     }
 5     
 6     func checkStraightLine(_ coordinates: [[Int]]) -> Bool {
 7         var coordinates = coordinates
 8         if coordinates.count < 2 {
 9             return false
10         }
11         
12         var first = coordinates.removeFirst()
13         var gradient: Double = 0.0
14         
15         for point in coordinates {
16             let currentGradient = getGradient(x2: point[0], x1: first[0], y2: point[1], y1: first[1])
17             if gradient == 0.0 {
18                 gradient = currentGradient
19             }
20             if gradient != currentGradient {
21                 return false
22             }
23         }
24         return true
25     }
26 }