Given a string s, find the length of the longest substring without repeating characters

Example Input: s = “abcabcbb” Output: 3 Explanation: The answer is “abc”, with the length of 3. I tried writing this but if condition is never being exceuted. I am not able to figure out the reason.

var lengthOfLongestSubstring = function(s) {
 let set = new Set();
    let c =0;
    for(let i =0; i< s.length; i++){
        if(set.has(s[i])){
            set.size =0;
        }
        else {
            console.log(c)
            c++;
        }
    }
    return c;
}; 
console.log(lengthOfLongestSubstring("abcabcbb"))

Answer

This is the same algorithm as described by danhuong, simply written with a recursive call and no mutable variables.

const longestSubstring = (str, i = 0, j = 0, found = new Set(), res = 0) =>
  j >= str.length
    ? res
  : found .has (str [j])
    ? longestSubstring (str, i + 1, j, found .delete (str [i]) && found, res)
    : longestSubstring (str, i, j + 1, found .add (str [j]), Math .max (res, j + 1 - i))

console .log (longestSubstring ("pwwkew"));
console .log (longestSubstring ("abcabcbb"));
console .log (longestSubstring ("abcabcbbvwxyz"));
console .log (longestSubstring ("abaca"));
console .log (longestSubstring ("abacdefg"));