Longest Substring Without Repeating Characters

Longest Substring Without Repeating Characters

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.

Example 4:

Input: s = ""
Output: 0

Constraints:

• 0 <= s.length <= 5 * 104

• s consists of English letters, digits, symbols and spaces.

Solutions

🧠 Cpp

class Solution {
public:
    int lengthOfLongestSubstring(string s)
    {
        if(s.empty())
            return 0;

        int res = 0;
        string substr = "";
        for(char ch : s)
        {
            auto ch_in_res_indx = substr.find(ch);
            if(ch_in_res_indx == std::string::npos)
                substr.push_back(ch);
            else
            {
                if(substr.size() > res)
                    res = substr.size();
                substr.erase(substr.begin(), substr.begin()+ch_in_res_indx+1);
                substr.push_back(ch);
            }
        }

        if(substr.size() > res)
                    res = substr.size();
        return res;

    }
};