[Swift]LeetCode3. 无重复字符的最长子串 | Longest Substring Without Repeating Characters

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" is a subsequence and not a substring.

示例 1:

输入: "abcabcbb"
输出: 3
解释: 无重复字符的最长子串是 "abc"，其长度为 3。

示例 2:

输入: "bbbbb"
输出: 1
解释: 无重复字符的最长子串是 "b"，其长度为 1。

示例 3:

输入: "pwwkew"
输出: 3
解释: 无重复字符的最长子串是 "wke"，其长度为 3。
     请注意，答案必须是一个子串，"pwke" 是一个子序列 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扩展方法
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 }

 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 }

 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  }

 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 }

 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  // 最大长度
 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 }

 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 }

 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 }

原文地址：https://www.cnblogs.com/strengthen/p/9858659.html