Longest Substring Without Repeating Characters

Leetcode#3

Longest Substring Without Repeating Characters

Problem Statement

Given a string s, find the length of the longest 

substring

 without repeating characters.

Example 1:

Input: s = "abcabcbb"
Output: 3
Explanation: The answer is "abc", with the length of 3.

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.

Golang Solution

func lengthOfLongestSubstring(s string) int {
	if len(s) == 0 {
		return 0
	}
	n := len(s)
	left := 0
	right := 0
	maxLen := 0
	seen := make(map[byte]int)

	for right < n {
		if prevIndex, found := seen[s[right]]; found {
			// if char is seen previously
			if prevIndex >= left {
				// jump directly to prevIndex + 1
				left = prevIndex + 1
			}
		}
		maxLen = max(maxLen, right-left+1)
		seen[s[right]] = right
		right++
	}

	return maxLen
}

Output

Input
s = "abcabcbb"
Output 
3

Input
s = "bbbbb"
Output
1

Input
s = "pwwkew"
Output
3

Input
s = "dvdf"
Output
3

Input
s = "ckilbkd"
Output
5

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