力扣 || 3.无重复字符的最长子串--Golang

func lengthOfLongestSubstring(s string) int {
	lft := 0	// left bound
	max := 0
	k := [256]int{}		// char -> last appear index after inserting into the window
	for rgt:=0; rgt<len(s); rgt++{
		if k[s[rgt]] > lft {lft = k[s[rgt]]}	// pop 0 or n
		k[s[rgt]] = rgt + 1						// push 1
		if max < rgt - lft + 1 { max = rgt - lft + 1 }
	}
	return max
}