Solution.go

func lengthOfLongestSubstring(s string) (ans int) {
	cnt := [128]int{}
	l := 0
	for r, c := range s {
		cnt[c]++
		for cnt[c] > 1 {
			cnt[s[l]]--
			l++
		}
		ans = max(ans, r-l+1)
	}
	return
}