Longest Substring Without Repeating Characters

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Given a string s, find the length of the longest

substringwithout 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.

You can solve this problem using the sliding window technique in JavaScript. Here's a possible implementation:

function lengthOfLongestSubstring(s) {
    let maxLength = 0;
    let charMap = new Map();
    let left = 0;

    for (let right = 0; right < s.length; right++) {
        const currentChar = s[right];

        if (charMap.has(currentChar) && charMap.get(currentChar) >= left) {
            // Move the left pointer to the right of the last occurrence of currentChar
            left = charMap.get(currentChar) + 1;
        }

        // Update the last seen index of the character
        charMap.set(currentChar, right);

        // Update the maximum length
        maxLength = Math.max(maxLength, right - left + 1);
    }

    return maxLength;
}

// Test cases
console.log(lengthOfLongestSubstring("abcabcbb")); // Output: 3
console.log(lengthOfLongestSubstring("bbbbb"));    // Output: 1
console.log(lengthOfLongestSubstring("pwwkew"));   // Output: 3

This function lengthOfLongestSubstring iterates through the string s using two pointers, left and right, to define a sliding window. It maintains a map charMap to store the most recent index of each character encountered. If a character is encountered again within the current substring, the left pointer is moved to the right of its last occurrence. Finally, the function returns the maximum length found.