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#