[Swift]LeetCode169. 求众数 | Majority Element

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Given an array of size n, find the majority element. The majority element is the element that appears more than ⌊ n/2 ⌋ times.

You may assume that the array is non-empty and the majority element always exist in the array.

Example 1:

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

Example 2:

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

---

给定一个大小为 n 的数组，找到其中的众数。众数是指在数组中出现次数大于 ⌊ n/2 ⌋ 的元素。

你可以假设数组是非空的，并且给定的数组总是存在众数。

示例 1:

输入: [3,2,3]
输出: 3

示例 2:

输入: [2,2,1,1,1,2,2]
输出: 2

---

class Solution {
    func majorityElement(_ nums: [Int]) -> Int {
        var res:Int = 0
        var counts:Int = 0
        for n in nums
        {
            if counts == 0
            {
                res = n
                counts = 1
            }
            else if res == n
            {
                counts += 1
            }
            else 
            {
                counts -= 1
            }
        }
        return res
    }
}

---

24ms

class Solution {
    func majorityElement(_ nums: [Int]) -> Int {
        var count = 1
        var pre = nums[0]
        var result = pre
        for i in 1..<nums.count {
            if count == 0 {
                count = 1
                pre = nums[i]
                result = nums[i]
            } else if pre == nums[i] {
                count += 1
            } else {
                count -= 1
            }
            
        }
        
        return result
         
    }
}

---

20ms

class Solution {
    func majorityElement(_ nums: [Int]) -> Int {
        guard nums.count > 0 else { return 0 }
        var candidate = nums[0]
        var times = 1
        var i = 1
        while i < nums.count {
            if times == 0 {
                candidate = nums[i]
                times = 1
                i += 1
                continue
            }
            if nums[i] == candidate {
                times += 1
            } else {
                times -= 1
            }
            i += 1
        }
        return candidate
    }
}

---

28ms

class Solution {
    func majorityElement(_ nums: [Int]) -> Int {
        var curNum = nums[0]
        var majority = 0;
        
        for num in 0..<nums.count {
            let val = nums[num]
            if curNum != val {
                majority -= 1
                if majority < 1 {
                    curNum = val
                    majority = 1
                }
            } else {
                majority += 1
            }
        }
        return curNum;
    }
}