[Swift]LeetCode228. 汇总区间 | Summary Ranges

★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★
➤微信公众号：山青咏芝（shanqingyongzhi）
➤博客园地址：山青咏芝（https://www.cnblogs.com/strengthen/）
➤GitHub地址：https://github.com/strengthen/LeetCode
➤原文地址：https://www.cnblogs.com/strengthen/p/10204442.html 
➤如果链接不是山青咏芝的博客园地址，则可能是爬取作者的文章。
➤原文已修改更新！强烈建议点击原文地址阅读！支持作者！支持原创！
★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★

热烈欢迎，请直接点击！！！

进入博主App Store主页，下载使用各个作品！！！

注：博主将坚持每月上线一个新app！！！

Given a sorted integer array without duplicates, return the summary of its ranges.

Example 1:

Input:  [0,1,2,4,5,7]
Output: ["0->2","4->5","7"]
Explanation: 0,1,2 form a continuous range; 4,5 form a continuous range.

Example 2:

Input:  [0,2,3,4,6,8,9]
Output: ["0","2->4","6","8->9"]
Explanation: 2,3,4 form a continuous range; 8,9 form a continuous range.

---

给定一个无重复元素的有序整数数组，返回数组区间范围的汇总。

示例 1:

输入: [0,1,2,4,5,7]
输出: ["0->2","4->5","7"]
解释: 0,1,2 可组成一个连续的区间; 4,5 可组成一个连续的区间。

示例 2:

输入: [0,2,3,4,6,8,9]
输出: ["0","2->4","6","8->9"]
解释: 2,3,4 可组成一个连续的区间; 8,9 可组成一个连续的区间。

---

8ms

class Solution {
    func summaryRanges(_ nums: [Int]) -> [String] {
        
        var resultArr = [String]()
        var tempValue = 0
        for (index ,value) in nums.enumerated() {
            var tempStr = "\(value)"
            if index == 0 {
                tempValue = value
                resultArr.append(tempStr)
            }else{
                if value == nums[index - 1] + 1 {
                    tempStr = "\(tempValue)->\(value)"
                    resultArr.removeLast()
                    resultArr.append(tempStr)
                }else{
                    tempValue = value
                    resultArr.append(tempStr)
                }
            }
            
        }
        return resultArr
    }
}

---

8ms

class Solution {
    func summaryRanges(_ nums: [Int]) -> [String] {
        if nums.count < 1 {
            return []
        }
        var ans = [String]()
        var first = nums[0]
        var lastV = first
        for i in 1..<nums.count {
            let cv = nums[i]
            if cv - lastV > 1 {
                let str = (lastV == first) ? "\(first)" : "\(first)->\(lastV)"
                ans.append(str)
                first = cv
            }
            lastV = cv
        }
        let str = (lastV == first) ? "\(first)" : "\(first)->\(lastV)"
        ans.append(str)
        return ans
    }
}

---

12ms

class Solution {
    func summaryRanges(_ nums: [Int]) -> [String] {
let n = nums.count
    if n == 0 {
        return [String]()
    }
    if n == 1 {
        return ["\(nums[0])"]
    }
    var temp = [String]()
    var start = 0
    var i = 0
    while i < n - 1 {
        if nums[i] == nums[i + 1] - 1 {
            i += 1
            if i == n - 1 {
                temp.append("\(nums[start])->\(nums[i])")
            }
            continue
        }
        if start == i {
            temp.append("\(nums[start])")
        } else {
            temp.append("\(nums[start])->\(nums[i])")
        }
        i += 1
        start = i
        if i == n - 1 {
            temp.append("\(nums[start])")
        }
    }
    return temp
    }
}

---

12ms

class Solution {
    func summaryRanges(_ nums: [Int]) -> [String] {
        if nums.isEmpty {
            return []
        }
        var res = [String]()
        
        var tmp = [nums[0]]
        
        for i in 1..<nums.count {
            let num = nums[i]
            if num == tmp.last! + 1 {
                tmp.append(num)
            }else {
                if tmp.count == 1 {
                    res.append("\(tmp[0])")
                }else {
                    res.append("\(tmp[0])->\(tmp.last!)")
                }
                tmp.removeAll()
                tmp.append(num)
            }
        }
        if tmp.count == 1 {
            res.append("\(tmp[0])")
        }else {
            res.append("\(tmp[0])->\(tmp.last!)")
        }
        
        return res
    }
}

---

16ms

class Solution {
    func summaryRanges(_ nums: [Int]) -> [String] {
        var result = [String]()
        guard nums.count > 0 else { return result }
        if nums.count == 1 { return ["\(nums[0])"] }
        var start = nums[0]
        var end = nums[0]
        for i in 1 ..< nums.count {
            let current = nums[i]
            if current != end + 1 {
                if start == end {
                    result.append("\(start)")
                } else {
                    result.append("\(start)->\(end)")
                }
                start = current
                end = current
            } else {
                end = current
            }
        }
        if start == end {
                result.append("\(start)")
        } else {
            result.append("\(start)->\(end)")
        }
        return result
    }
}

---

104ms

class Solution {
    func summaryRanges(_ nums: [Int]) -> [String] {
        var res = [String]()
        var str = ""
        var start = 0
        
        guard nums.count > 0 else {
            return res
        }
        
        for i in 0 ... nums.count {
            if i == nums.count || (i > 0 && nums[i] != nums[i - 1] + 1) {
                str = "\(nums[start])"
                if i - 1 != start {
                    str += "->\(nums[i - 1])"
                }
                res.append(str)
                start = i
            }
        }
        
        return res
    }
}