golang寻找最长不含有重复字符的子串

论：如何找出一个字符串种不重复的最长字串的长度？

package main

import (
   "fmt"
   "strings"
)

/*
   * 暴力穷举方：
           找出全部的无重复子串, 统计出最长的
*/
func lengthOfLongestSubstring(s string) int {
   count := 0
   sonStringMap := make(map[string]int)
   for j := 0; j < len(s); j++ {
      tmpString := s[j:]
      subString := ""
      for k, v := range []byte(tmpString) {
         if strings.Contains(subString, string(v)) {
            sonStringMap[subString]++
            if k == len(tmpString) {
               sonStringMap[subString]++
            }
            subString = ""
         } else {
            subString += string(v)
            if k == len(tmpString)-1 {
               sonStringMap[subString]++
            }
         }
      }
   }
   //fmt.Println(sonStringMap)
   for k, _ := range sonStringMap {
      if count < len(k) {
         count = len(k)
      }
   }
   return count
}

func lengthOfLongestSubstring1(s string) int {
   m := make(map[byte]int)
   res := 0
   left := 0
   for i := 0; i < len(s); i++ {
      if m[s[i]] > 0 && left < m[s[i]] {
         left = m[s[i]]
      }
      m[s[i]] = i + 1
      if i-left+1 > res {
         res = i - left + 1
      }
   }
   return res
}

func lengthOfLongestSubstring2(s string) int {
   m := make(map[byte]int)
   res := 0
   left := 0
   for i := 0; i < len(s); i++ {
      if m[[]byte(s)[i]] == 0 || m[[]byte(s)[i]] < left {
         res = func(a, b int) int {
            if a > b {
               return a
            }
            return b
         }(res, i-left+1)
      } else {
         left = m[s[i]]
      }
      m[s[i]] = i + 1
   }
   return res
}

//寻找最长不含有重复字符的子串，里面的rune直接把中文转为一个字节，中英文一起操作
func lengthOfLongestSubstring3(s string) int {
   lastOcc := make(map[rune]int) // map用于存放char index
   srart := 0
   maxLength := 0
   for i, ch := range []rune(s) {
      if lastI, ok := lastOcc[ch]; ok && lastI >= srart {
         srart = lastI + 1
      }

      if i-srart+1 > maxLength {
         maxLength = i - srart + 1
      }
      lastOcc[ch] = i
   }
   return maxLength
}

func main() {
   str := "abcdabsdkljlkdll122300GHJKLabcdUJMRFGHyhjmkecvxbwnjkmc;"
   fmt.Println(lengthOfLongestSubstring(str))
   fmt.Println(lengthOfLongestSubstring1(str))
   fmt.Println(lengthOfLongestSubstring2(str))
   fmt.Println(lengthOfLongestSubstring3(str))
}

执行：

root@ubuntu:~/zz# go run main.go 
20
20
20
20
root@ubuntu:~/zz#