[Swift]LeetCode1037. 有效的回旋镖 | Valid Boomerang

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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

---

回旋镖定义为一组三个点，这些点各不相同且不在一条直线上。

给出平面上三个点组成的列表，判断这些点是否可以构成回旋镖。

示例 1：

输入：[[1,1],[2,3],[3,2]]
输出：true

示例 2：

输入：[[1,1],[2,2],[3,3]]
输出：false

提示：

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

---

8ms

class Solution {
    func isBoomerang(_ points: [[Int]]) -> Bool {
        let x1 = points[0][0]
        let x2 = points[0][1]
        let y1 = points[1][0]
        let y2 = points[1][1]
        let z1 = points[2][0]
        let z2 = points[2][1]

        // A/B=C/D => AD=BC
        let kXY = (x1 - y1) * (x2 - z2)
        let kXZ = (x2 - y2) * (x1 - z1)
        return kXY != kXZ
    }
}

---

Runtime: 12 ms

Memory Usage: 19.2 MB

class Solution {
    func isBoomerang(_ points: [[Int]]) -> Bool {
        let set:Set<[Int]> = Set(points)
        if set.count != points.count
        {
            return false
        }
        let point1:[Int] = points[0]
        let point2:[Int] = points[1]
        let point3:[Int] = points[2]
        return getSlope(point1, point2) != getSlope(point2, point3)
    }
    
    func getSlope(_ point1:[Int],_ point2:[Int]) -> Double
    {
        return Double(point2[1] - point1[1]) / Double(point2[0] - point1[0])
    }
}

---

12ms

class Solution {
    func isBoomerang(_ points: [[Int]]) -> Bool {
        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]);
        return area != 0;
    }
}