[Swift]LeetCode1037. 有效的迴旋鏢 | Valid Boomerang

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➤微信公衆號：山青詠芝（shanqingyongzhi）
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➤GitHub地址：https://github.com/strengthen/LeetCode
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A boomerang is a set of 3 points that are all distinct and not in a straight line.

Given a list of three points in the plane, return whether these points are a boomerang.

Example 1:

Input: [[1,1],[2,3],[3,2]]
Output: true 

Example 2:

Input: [[1,1],[2,2],[3,3]]
Output: false

Note:

1. points.length == 3
2. points[i].length == 2
3. 0 <= points[i][j] <= 100

---

迴旋鏢定義爲一組三個點，這些點各不相同且不在一條直線上。

給出平面上三個點組成的列表，判斷這些點是否能夠構成迴旋鏢。

示例 1：

輸入：[[1,1],[2,3],[3,2]]
輸出：true

示例 2：

輸入：[[1,1],[2,2],[3,3]]
輸出：false

提示：

1. points.length == 3
2. points[i].length == 2
3. 0 <= points[i][j] <= 100

---

8ms

 1 class Solution {
 2     func isBoomerang(_ points: [[Int]]) -> Bool {
 3         let x1 = points[0][0]
 4         let x2 = points[0][1]
 5         let y1 = points[1][0]
 6         let y2 = points[1][1]
 7         let z1 = points[2][0]
 8         let z2 = points[2][1]
 9 
10         // A/B=C/D => AD=BC
11         let kXY = (x1 - y1) * (x2 - z2)
12         let kXZ = (x2 - y2) * (x1 - z1)
13         return kXY != kXZ
14     }
15 }

---

Runtime: 12 ms

Memory Usage: 19.2 MB

 1 class Solution {
 2     func isBoomerang(_ points: [[Int]]) -> Bool {
 3         let set:Set<[Int]> = Set(points)
 4         if set.count != points.count
 5         {
 6             return false
 7         }
 8         let point1:[Int] = points[0]
 9         let point2:[Int] = points[1]
10         let point3:[Int] = points[2]
11         return getSlope(point1, point2) != getSlope(point2, point3)
12     }
13     
14     func getSlope(_ point1:[Int],_ point2:[Int]) -> Double
15     {
16         return Double(point2[1] - point1[1]) / Double(point2[0] - point1[0])
17     }
18 }

---

12ms

 

1 class Solution {
2     func isBoomerang(_ points: [[Int]]) -> Bool {
3         var area = points[0][0]*(points[1][1]-points[2][1])+points[1][0]*(points[2][1]-points[0][1])+points[2][0]*(points[0][1]-points[1][1]);
4         return area != 0;
5     }
6 }