[Swift]LeetCode228. 彙總區間 | Summary Ranges

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➤微信公衆號：山青詠芝（shanqingyongzhi）
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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.

---

給定一個無重複元素的有序整數數組，返回數組區間範圍的彙總。

示例 1:

輸入: [0,1,2,4,5,7]
輸出: ["0->2","4->5","7"]
解釋: 0,1,2 可組成一個連續的區間; 4,5 可組成一個連續的區間。

示例 2:

輸入: [0,2,3,4,6,8,9]
輸出: ["0","2->4","6","8->9"]
解釋: 2,3,4 可組成一個連續的區間; 8,9 可組成一個連續的區間。

---

8ms

 1 class Solution {
 2     func summaryRanges(_ nums: [Int]) -> [String] {
 3         
 4         var resultArr = [String]()
 5         var tempValue = 0
 6         for (index ,value) in nums.enumerated() {
 7             var tempStr = "\(value)"
 8             if index == 0 {
 9                 tempValue = value
10                 resultArr.append(tempStr)
11             }else{
12                 if value == nums[index - 1] + 1 {
13                     tempStr = "\(tempValue)->\(value)"
14                     resultArr.removeLast()
15                     resultArr.append(tempStr)
16                 }else{
17                     tempValue = value
18                     resultArr.append(tempStr)
19                 }
20             }
21             
22         }
23         return resultArr
24     }
25 }

---

8ms

 1 class Solution {
 2     func summaryRanges(_ nums: [Int]) -> [String] {
 3         if nums.count < 1 {
 4             return []
 5         }
 6         var ans = [String]()
 7         var first = nums[0]
 8         var lastV = first
 9         for i in 1..<nums.count {
10             let cv = nums[i]
11             if cv - lastV > 1 {
12                 let str = (lastV == first) ? "\(first)" : "\(first)->\(lastV)"
13                 ans.append(str)
14                 first = cv
15             }
16             lastV = cv
17         }
18         let str = (lastV == first) ? "\(first)" : "\(first)->\(lastV)"
19         ans.append(str)
20         return ans
21     }
22 }

---

12ms

 1 class Solution {
 2     func summaryRanges(_ nums: [Int]) -> [String] {
 3 let n = nums.count
 4     if n == 0 {
 5         return [String]()
 6     }
 7     if n == 1 {
 8         return ["\(nums[0])"]
 9     }
10     var temp = [String]()
11     var start = 0
12     var i = 0
13     while i < n - 1 {
14         if nums[i] == nums[i + 1] - 1 {
15             i += 1
16             if i == n - 1 {
17                 temp.append("\(nums[start])->\(nums[i])")
18             }
19             continue
20         }
21         if start == i {
22             temp.append("\(nums[start])")
23         } else {
24             temp.append("\(nums[start])->\(nums[i])")
25         }
26         i += 1
27         start = i
28         if i == n - 1 {
29             temp.append("\(nums[start])")
30         }
31     }
32     return temp
33     }
34 }

---

12ms

 1 class Solution {
 2     func summaryRanges(_ nums: [Int]) -> [String] {
 3         if nums.isEmpty {
 4             return []
 5         }
 6         var res = [String]()
 7         
 8         var tmp = [nums[0]]
 9         
10         for i in 1..<nums.count {
11             let num = nums[i]
12             if num == tmp.last! + 1 {
13                 tmp.append(num)
14             }else {
15                 if tmp.count == 1 {
16                     res.append("\(tmp[0])")
17                 }else {
18                     res.append("\(tmp[0])->\(tmp.last!)")
19                 }
20                 tmp.removeAll()
21                 tmp.append(num)
22             }
23         }
24         if tmp.count == 1 {
25             res.append("\(tmp[0])")
26         }else {
27             res.append("\(tmp[0])->\(tmp.last!)")
28         }
29         
30         return res
31     }
32 }

---

16ms

 1 class Solution {
 2     func summaryRanges(_ nums: [Int]) -> [String] {
 3         var result = [String]()
 4         guard nums.count > 0 else { return result }
 5         if nums.count == 1 { return ["\(nums[0])"] }
 6         var start = nums[0]
 7         var end = nums[0]
 8         for i in 1 ..< nums.count {
 9             let current = nums[i]
10             if current != end + 1 {
11                 if start == end {
12                     result.append("\(start)")
13                 } else {
14                     result.append("\(start)->\(end)")
15                 }
16                 start = current
17                 end = current
18             } else {
19                 end = current
20             }
21         }
22         if start == end {
23                 result.append("\(start)")
24         } else {
25             result.append("\(start)->\(end)")
26         }
27         return result
28     }
29 }

---

104ms

 1 class Solution {
 2     func summaryRanges(_ nums: [Int]) -> [String] {
 3         var res = [String]()
 4         var str = ""
 5         var start = 0
 6         
 7         guard nums.count > 0 else {
 8             return res
 9         }
10         
11         for i in 0 ... nums.count {
12             if i == nums.count || (i > 0 && nums[i] != nums[i - 1] + 1) {
13                 str = "\(nums[start])"
14                 if i - 1 != start {
15                     str += "->\(nums[i - 1])"
16                 }
17                 res.append(str)
18                 start = i
19             }
20         }
21         
22         return res
23     }
24 }