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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: 3Explanation: The answer is "abc", with the length of 3.

Example 2:

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

Example 3:

Input: s = "pwwkew"Output: 3Explanation: 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.

My solution​

/**
 * @param {string} s
 * @return {number}
 */
var lengthOfLongestSubstring = function(s) {
    let start = 0;
    let end = 0;
    let memo = new Set();
    let count = Number.MIN_SAFE_INTEGER;
    
    while (end < s.length) {
        const char = s.charAt(end);
        
        if (memo.has(char)) {
            while (memo.has(char)) {
                const firstChar = s.charAt(start);
                memo.delete(firstChar);
                start++
            }
        }
        else {
            memo.add(char);
            const len = end - start + 1;
            count = Math.max(len, count)
            end++
        }
    }
    
    return count === Number.MIN_SAFE_INTEGER ? 0 : count;
};