[Swift]LeetCode384. 打乱数组 | Shuffle an Array

原文地址：https://www.cnblogs.com/strengthen/p/10283261.html 

Shuffle a set of numbers without duplicates.

Example:

// Init an array with set 1, 2, and 3.
int[] nums = {1,2,3};
Solution solution = new Solution(nums);

// Shuffle the array [1,2,3] and return its result. Any permutation of [1,2,3] must equally likely to be returned.
solution.shuffle();

// Resets the array back to its original configuration [1,2,3].
solution.reset();

// Returns the random shuffling of array [1,2,3].
solution.shuffle();

---

打乱一个没有重复元素的数组。

示例:

// 以数字集合 1, 2 和 3 初始化数组。
int[] nums = {1,2,3};
Solution solution = new Solution(nums);

// 打乱数组 [1,2,3] 并返回结果。任何 [1,2,3]的排列返回的概率应该相同。
solution.shuffle();

// 重设数组到它的初始状态[1,2,3]。
solution.reset();

// 随机返回数组[1,2,3]打乱后的结果。
solution.shuffle();

---

676ms

class Solution {
    var nums:[Int]
    var oriNums:[Int]
    init(_ nums: [Int]) {
        self.nums = nums
        self.oriNums = nums
    }
    
    /** Resets the array to its original configuration and return it. */
    func reset() -> [Int] {
        return self.oriNums   
    }
    
    /** Returns a random shuffling of the array. */
    func shuffle() -> [Int] {
        for i in 0..<nums.count/2
        {
            var t:Int = Int.random(in:0..<(nums.count))
            //法1：
            //(nums[i], nums[t]) = (nums[t],nums[i])
            //法2：
            nums.swapAt(i,t);
        }
        return nums
    }  
}

/**
 * Your Solution object will be instantiated and called as such:
 * let obj = Solution(nums)
 * let ret_1: [Int] = obj.reset()
 * let ret_2: [Int] = obj.shuffle()
 */
 

---

704ms

class Solution {

    var original: [Int]
    var shuffable: [Int]
    init(_ nums: [Int]) {
        self.original = nums
        self.shuffable = nums
    }
    
    /** Resets the array to its original configuration and return it. */
    func reset() -> [Int] {
      return original
    }
    
    /** Returns a random shuffling of the array. */
    func shuffle() -> [Int] {
        shuffable.shuffle()
        return shuffable
    }
}

/**
 * Your Solution object will be instantiated and called as such:
 * let obj = Solution(nums)
 * let ret_1: [Int] = obj.reset()
 * let ret_2: [Int] = obj.shuffle()
 */

---

760ms

class Solution {
    var a = [Int]()
    init(_ nums: [Int]) {
        a = nums
    }
    
    /** Resets the array to its original configuration and return it. */
    func reset() -> [Int] {
      return a
    }
    
    /** Returns a random shuffling of the array. */
    func shuffle() -> [Int] {
        if a == []{return a}
        return shuffle0()
    }
    func shuffle0() -> [Int] {
        var data:[Int] = a
        for i in 0..<a.count {
            let index = Int.random(in: 0 ... i)
            if index != i {
                (data[i] , data[index]) = (data[index] , data[i])
            }
        }
        return data
    }
}

/**
 * Your Solution object will be instantiated and called as such:
 * let obj = Solution(nums)
 * let ret_1: [Int] = obj.reset()
 * let ret_2: [Int] = obj.shuffle()
 */

---

828ms

class Solution {
    var interges: [Int]
    init(_ nums: [Int]) {
        self.interges = nums
    }
    /** Resets the array to its original configuration and return it. */
    func reset() -> [Int] {
        return interges
    }
    /** Returns a random shuffling of the array. */
    func shuffle() -> [Int] {
        var shuffled = interges
        var cursorL = shuffled.startIndex
        let cursorR = shuffled.index(before: interges.endIndex)
        while cursorL < cursorR {
            let steps = shuffled.distance(from: cursorL, to: cursorR)
            let randomStep = Int.random(in: 0...steps)
            let offsetIndex = shuffled.index(cursorL, offsetBy: randomStep)
            shuffled.swapAt(cursorL, offsetIndex)
            shuffled.formIndex(after: &cursorL)
        }
        return shuffled
    }
}

---

860ms

class Solution {
var num: [Int]
    
    init(_ nums: [Int]) {
        self.num = nums
    }
    
    /** Resets the array to its original configuration and return it. */
    func reset() -> [Int] {
        return self.num
    }
    
    /** Returns a random shuffling of the array. */
    func shuffle() -> [Int] {
        return self.num.shuffled() 
    }
}