0003-longest-substring-without-repeating-characters.go

func lengthOfLongestSubstring(s string) int {
    charSet := make(map[byte]bool)
    l := 0
    res := 0
    
    for r, _ := range s {
        for charSet[s[r]] {
            delete(charSet,s[l])
            l++
        }
        charSet[s[r]] = true
        res = max(res, r-l+1)
    }
    return res
}

func max(a,b int) int {
    if a > b{
        return a
    }
    return b
}