Given a string, find the length of the longest substring without repeating characters.

Examples:

Given "abcabcbb", the answer is "abc", which the length is 3.

Given "bbbbb", the answer is "b", with the length of 1.

Given "pwwkew", the answer is "wke", with the length of 3. Note that the answer must be a substring, "pwke"

給定一個字符串，找出不含有重復字符的最長子串的長度。

示例 1:

輸入: "abcabcbb"
輸出: 3 
解釋: 無重復字符的最長子串是 "abc"，其長度為 3。

示例 2:

輸入: "bbbbb"
輸出: 1
解釋: 無重復字符的最長子串是 "b"，其長度為 1。

示例 3:

輸入: "pwwkew"
輸出: 3
解釋: 無重復字符的最長子串是 "wke"，其長度為 3。
     請註意，答案必須是一個子串，"pwke" 是一個子序列 而不是子串。

36ms

 1 class Solution {
 2     func lengthOfLongestSubstring(_ s: String) -> Int {
 3         var m:[Int] = [Int](repeating: -1,count: 256)
 4         var res:Int = 0, left:Int = -1
 5         for i in 0..<s.count
 6         {
 7             let num:Int = s[s.index(s.startIndex,offsetBy: i)].toInt()
 
 8             left = max(left,m[num])
 9             m[num] = i
10             res = max(res,i - left)
11         }
12         return res
13     }
14 }
15 //Character擴展方法  
16 extension Character  
17 {  
18     func toInt() -> Int  
19     {  
20         var num:Int = Int()
21         for scalar in String(self).unicodeScalars  
22         {  
23             num = Int(scalar.value)  
24         }  
25         return num  
26     }  
27 }

20ms

 1 class Solution {
 2  func lengthOfLongestSubstring(_ s: String) -> Int {
 3      var right = 1
 4      var left = 0
 5      var i = 0
 6      var result = 0
 7      
 8      if s.count > 0 {
 9          result = right - left
10          let chars = Array(s.utf8)
11          
12          //Interate in a incremental window 
13          while right < chars.count {
14              i = left
15                 while i < right {
16                     //Check if a duplicate is found
17                     if chars[i] == chars[right] {
18                         left = i + 1
19                         break
20                     } 
21                 i = i + 1
22              }
23          result = max(result,right-left+1)     
24          right = right + 1
25      }
26      }
27      return result
28      }
29 }

28ms

 1 class Solution {
 2  func lengthOfLongestSubstring(_ s: String) -> Int {
 3         if s.characters.count == 0 {
 4             return 0
 5         }
 6         
 7         let chars = Array(s.utf8)
 8         var left = 0
 9         var right = 1
10         var result = right - left
11         var i = 0
12         
13         while right < chars.count {
14             i = left
15             while i < right {
16                 if chars[i] == chars[right] {
17                     left = i + 1
18                     break
19                 }
20                 i += 1
21             }
22             result = max(result, right - left + 1)
23             right += 1
24         }
25         
26         return result
27     }
28  }

36ms

 1 class Solution {
 2     func lengthOfLongestSubstring(_ s: String) -> Int {
 3         var arr = [Int](repeating: -1, count: 256)
 4         var s = Array(s)
 5         var currentLength = 0
 6         var maxLength = 0
 7         for i in 0..<s.count {
 8             let cValue = Int(s[i].unicodeScalars.first!.value)
 9             let preIndex = arr[cValue]
10             if arr[cValue] == -1 || i - preIndex > currentLength {
11                 currentLength += 1
12             } else {
13                 maxLength = max(currentLength, maxLength)
14                 currentLength = i - preIndex
15             }
16             arr[cValue] = i
17         }
18         
19         maxLength = max(currentLength, maxLength)
20         return maxLength
21     }
22 }

44ms

 1 class Solution {
 2     func lengthOfLongestSubstring(_ s: String) -> Int {
 3         
 4         var last:[Int] = Array.init(repeating: -1, count: 127)
 5         var start: Int = 0 // 起始位置
 6         var maxLength: Int = 0  // 最大長度
 7         
 8         let chars: [Int8]? = s.cString(using: String.Encoding.utf8)
 9         
10         for i in 0..<s.count {
11             
12             let hash_i: Int = Int(chars![i])
13             let hash_null: Int = 0
14             
15             if (last[hash_i - hash_null] >= start) {
16                 maxLength = max(maxLength, i-start)
17                 start = last[hash_i - hash_null] + 1
18             }
19             last[hash_i - hash_null] = i
20         }
21         maxLength = max(maxLength, s.count - start)
22         return maxLength
23     }
24 }

52ms

 1 class Solution {
 2     func lengthOfLongestSubstring(_ s: String) -> Int {
 3         let charArr = Array(s)
 4         let len = s.count
 5         var ans = 0
 6         var index = Array.init(repeating: 0, count: 128)
 7         var j = 0
 8         for i in 0..<len {
 9             let char = charArr[i]
10             if let v = char.unicodeScalars.first?.value {
11                 j = max(index[Int(v)], j)
12                 ans = max(ans, i - j + 1)
13                 index[Int(v)] = i + 1
14             }
15         }
16         return ans
17     }
18 }

84ms

 1 class Solution {
 2     func lengthOfLongestSubstring(_ s: String) -> Int {
 3         let cs = s.cString(using: .utf8)
 4         guard var chars = cs else { return 0 }
 5         guard chars.count > 1 else {
 6             return 0
 7         }
 8         chars.removeLast()
 9         var maxCount: Int = 0
10         var i = 0, j = 0
11         var map: [Int8: Int] = [:]
12         while j < chars.count {
13             if map.keys.contains(chars[j]) {
14                 i = max(map[chars[j]] ?? 0, i)
15             }
16             maxCount = max(maxCount, j - i + 1)
17             map[chars[j]] = j + 1
18             j += 1
19         }
20         return maxCount
21     }
22 }

[Swift]LeetCode3. 無重復字符的最長子串 | Longest Substring Without Repeating Characters