[Swift]LeetCode219. 存在重复元素 II | Contains Duplicate II

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Given an array of integers and an integer k, find out whether there are two distinct indices i and j in the array such that nums[i] = nums[j] and the absolute difference between i and j is at most k.

Example 1:

Input: nums = [1,2,3,1], k = 3
Output: true

Example 2:

Input: nums = [1,0,1,1], k = 1
Output: true

Example 3:

Input: nums = [1,2,3,1,2,3], k = 2
Output: false

---

给定一个整数数组和一个整数 k，判断数组中是否存在两个不同的索引 i 和 j，使得 nums [i] = nums [j]，并且 i 和 j 的差的绝对值最大为 k。

示例 1:

输入: nums = [1,2,3,1], k= 3
输出: true

示例 2:

输入: nums = [1,0,1,1], k=1
输出: true

示例 3:

输入: nums = [1,2,3,1,2,3], k=2
输出: false

---

class Solution {
    func containsNearbyDuplicate(_ nums: [Int], _ k: Int) -> Bool {
        //判断
        if nums == nil || nums.count < 2 || k < 1
        {
            return false
        }
        var map:[Int:Int] = [Int:Int]()
        for i in 0..<(nums.count)
        {
            if map.keys.contains(nums[i])
            {
                var sub:Int = i - map[nums[i]]!
                if sub <= k
                {
                    return true
                }
                else
                {
                    map[nums[i]] = i
                }
            }
            else
            {
                map[nums[i]] = i
            }
        }
        return false
    }
}

---

32ms

class Solution {
    func containsNearbyDuplicate(_ nums: [Int], _ k: Int) -> Bool {
        var set = Set<Int>()
        for i in 0..<nums.count {
            if i > k { set.remove(nums[i - k - 1]) }
            if !set.insert(nums[i]).inserted { return true }
        }
        return false
    }
}

---

32ms

class Solution {
    func containsNearbyDuplicate(_ nums: [Int], _ k: Int) -> Bool {
        var set = Set<Int>()
        
        for i in 0..<nums.count {
            if i > k {
                set.remove(nums[i - k - 1])
            }
            if !set.insert(nums[i]).inserted {
                return true
            }
        }
        
        return false
    }
}

---

40ms

class Solution {
    func containsNearbyDuplicate(_ nums: [Int], _ k: Int) -> Bool {
        var map: [Int:Int] = [:]
        
        for i in 0..<nums.count {
            if let index = map[nums[i]], i - index <= k {
                return true
            } else {
                map[nums[i]] = i
            }
        }
        
        return false
    }
}

---

44ms

class Solution {
    func containsNearbyDuplicate(_ nums: [Int], _ k: Int) -> Bool {
        var set: Set<Int> = []
        for i in 0..<nums.count {
            if i > k {
                set.remove(nums[i-k-1])//移掉无效数据
            }
            if !set.insert(nums[i]).inserted {
                return true
            }
        }
        return false
    }
}