[Swift]LeetCode447. 回旋镖的数量 | Number of Boomerangs

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Given n points in the plane that are all pairwise distinct, a "boomerang" is a tuple of points (i, j, k) such that the distance between i and j equals the distance between i and k (the order of the tuple matters).

Find the number of boomerangs. You may assume that n will be at most 500 and coordinates of points are all in the range [-10000, 10000] (inclusive).

Example:

Input:
[[0,0],[1,0],[2,0]]

Output:
2

Explanation:
The two boomerangs are [[1,0],[0,0],[2,0]] and [[1,0],[2,0],[0,0]]

---

给定平面上 n 对不同的点，“回旋镖” 是由点表示的元组 (i, j, k) ，其中 i 和 j 之间的距离和 i 和 k 之间的距离相等（需要考虑元组的顺序）。

找到所有回旋镖的数量。你可以假设 n 最大为 500，所有点的坐标在闭区间 [-10000, 10000] 中。

示例:

输入:
[[0,0],[1,0],[2,0]]

输出:
2

解释:
两个回旋镖为 [[1,0],[0,0],[2,0]] 和 [[1,0],[2,0],[0,0]]

---

792ms

class Solution {   
    func numberOfBoomerangs(_ points: [[Int]]) -> Int
    {
        var sum = 0

        for x in 0..<points.count {
            let m = points[x]
            
            var dic:Dictionary<Double,Int> = Dictionary.init()

            for y in 0..<points.count{
                let n = points [y]
                let p = m[0] - n[0]
                let q = m[1] - n[1]
                let k = sqrt(pow(Double(p), 2)+pow(Double(q), 2))
                var z = dic[k]
                if z == nil{
                    z = 0
                }
                sum += z!*2
                dic[k] = z! + 1
            }
        }      
        return sum
    }
}

---

1072ms

class Solution {
    func numberOfBoomerangs(_ points: [[Int]]) -> Int {
        let length = points.count
        guard length > 0 else {
            return 0
        }
        var count = 0
        
        for i in 0..<length {
            var distanceInfo = Dictionary<Int,Int>()
            
            // 找出与i距离相同的点
            for j in 0..<length {
                if i != j {
                    let distance = self.distance(points[i], points[j])
                    if let tempCount = distanceInfo[distance] {
                        distanceInfo[distance] = tempCount + 1
                    } else {
                        distanceInfo[distance] = 1
                    }
                }
            }
            
            // 遍历字典，同i的距离相同的点大于2个
            for (_, countOfDistance) in distanceInfo {
                count += (countOfDistance * (countOfDistance - 1))
            }
            
        }
        
        return count
    }
    
    func distance(_ point1: [Int], _ point2: [Int]) -> Int {
        let x = point1[0] - point2[0]
        let y = point1[1] - point2[1]
        
        return x * x + y * y
    }
}

---

1204ms

class Solution {
    func numberOfBoomerangs(_ points: [[Int]]) -> Int {
        var res:Int = 0
        for i in 0..<points.count
        {
            var m:[Int:Int] = [Int:Int]()
            for j in 0..<points.count
            {
                var a:Int = points[i][0] - points[j][0]
                var b:Int = points[i][1] - points[j][1]
                if m[a * a + b * b] == nil
                {
                     m[a * a + b * b] = 1
                }
                else
                {
                     m[a * a + b * b]! += 1
                }               
            }
            
            for val in m.values
            {
                res += val * (val - 1);
            }
        }
        return res
    }
}

---

1208ms

class Solution {
    func numberOfBoomerangs(_ points: [[Int]]) -> Int {
        var result = 0
        for index in 0..<points.count {
            var map: [Int: Int] = [:]
            for index2 in 0..<points.count {
                if index2 == index {
                    continue
                }

                let distance = getDistance(points[index], points[index2])
                if let count = map[distance] {
                    map[distance] = count + 1
                } else {
                    map[distance] = 1
                }
            }
            
            for count in map.values {
                result += count * (count - 1)
            }
        }

        return result
    }

    func getDistance(_ point: [Int], _ point2: [Int]) -> Int {
        let x = point[0] - point2[0]
        let y = point[1] - point2[1]
        return x * x + y * y
    }
}

---

1560ms

class Solution {
    func numberOfBoomerangs(_ points: [[Int]]) -> Int {  
        func getDistance(_ a: [Int], _ b: [Int]) -> Int {
            return (a[0] - b[0]) * (a[0] - b[0]) + (a[1] - b[1]) * (a[1] - b[1])
        }        
        var map = [Int: Int]()
        var res = 0        
        for i in 0..<points.count {
            for j in 0..<points.count {
                if i == j { continue }                
                let distance = getDistance(points[i], points[j])                
                map[distance] = (map[distance] ?? 0) + 1
            }            
            for values in map.values {
                res += values * (values - 1)
            }
            map.removeAll()
        }
        return res
    }   
}