3. 无重复字符的最长子串

package main
import (
    "fmt"
)
func lengthOfLongestSubstring4(s string) int {
    freq := make([]int,128)
    var res = 0
    start,end := 0,-1
    for start<len(s){
        if end+1<len(s)&&freq[s[end+1]] == 0{
            end++
            freq[s[end]]++
        }else{
            freq[s[start]]--
            start++
        }
        res = max(res,end-start+1)
    }
    return res
}
func max(i,j int)int{
    if i>j{
        return i
    }else{
        return j
    }
}
func lengthOfLongestSubstring2(s string) int{
    m :=make(map[byte]int) //定义map
    max :=0
    start :=0
    for i :=range s{
        v,ok := m[s[i]]
        if ok {
            j := start
            for ;j<=v;j++{
                delete(m,s[j])
            }
            start =j
        }
        m[s[i]] = i
        if max<i-start+1 {
            max = i-start+1
        }
    }
    return max
}
func lengthOfLongestSubstring3(s string) int{
    m := make(map[byte]int)
    var r []byte //窗口数据
    l :=0
    for i :=range s{
        if j,ok:=m[s[i]];ok {
            if i-j>len(r) {
                r =r[i-j:]
            }
        }else {
            r = append(r,s[i])
        }
        m[s[i]] = i
        l = max(l,len(r))
    }
    return l
}
func lengthOfLongestSubstring1(s string) int{
    if len(s)==0 {
        return 0
    }
    ans := 0 // 默认就是1了
    m := map[byte]int{}
    start := -1
    for i:=0 ;i<len(s);i++{// 遍历字符串
        if index,ok := m[s[i]];ok {//存在
            start = max(start,index)//但是要保证起始索引是递增的
        }
        ans = max(ans,i-start)
        m[s[i]]=i
    }
    return ans
}
func main() {
    fmt.Println(lengthOfLongestSubstring(""))//1
    fmt.Println(lengthOfLongestSubstring1("au"))//2
    fmt.Println(lengthOfLongestSubstring1("abcabcbb"))//3
    fmt.Println(lengthOfLongestSubstring1("bbbb"))//1
    fmt.Println(lengthOfLongestSubstring1("pwwkew"))//3
    fmt.Println(lengthOfLongestSubstring1("abba"))//2
    fmt.Println(lengthOfLongestSubstring1("bpfbhmipx"))//7
    fmt.Println(lengthOfLongestSubstring1("eeydgwdykpv"))//7
}