Longest Substring Without Repeating Characters

LeetCode 3 · View on LeetCode

Variable-size window with a map tracking the last index of each character. When a duplicate is found, jump the left pointer past it.

package main

import "fmt"

func lengthOfLongestSubstring(s string) int {
	seen := make(map[byte]int)
	maxLen, left := 0, 0

	for right := 0; right < len(s); right++ {
		if idx, ok := seen[s[right]]; ok && idx >= left {
			left = idx + 1
		}
		seen[s[right]] = right
		if right-left+1 > maxLen {
			maxLen = right - left + 1
		}
	}
	return maxLen
}

func main() {
	fmt.Println(lengthOfLongestSubstring("abcabcbb")) // 3
	fmt.Println(lengthOfLongestSubstring("bbbbb"))    // 1
	fmt.Println(lengthOfLongestSubstring("pwwkew"))   // 3
}