package main

import "fmt"

/*
 * Given a string s, find the length of the longest substring without duplicate characters.

 Example 1:
 Input: s = "abcabcbb"
 Output: 3
 Explanation: The answer is "abc", with the length of 3. Note that "bca" and "cab" are also correct answers.

 Example 2:
 Input: s = "bbbbb"
 Output: 1
 Explanation: The answer is "b", with the length of 1.

 Example 3:
 Input: s = "pwwkew"
 Output: 3
 Explanation: The answer is "wke", with the length of 3.
 Notice that the answer must be a substring, "pwke" is a subsequence and not a substring.


 Constraints:
 0 <= s.length <= 5 * 104
 s consists of English letters, digits, symbols and spaces.
*/

func lengthOfLongestSubstring(s string) int {
	lastSeen := make(map[rune]int, len(s))
	maxLength := 0
	left := 0
	for right, char := range s {
		if previndex, ok := lastSeen[char]; previndex >= left && ok {
			left = previndex + 1
		}
		lastSeen[char] = right
		currentLength := right - left + 1
		if currentLength > maxLength {
			maxLength = currentLength
		}
	}
	return maxLength
}

func main() {
	s := "pwwkew"
	fmt.Println(lengthOfLongestSubstring(s))
}


Longest-substring

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