Longest Substring Without Repeating Characters LeetCode Solution

Here, We see Longest Substring Without Repeating Characters problem Solution. This Leetcode problem is done in many programming languages like C++, Java, JavaScript, Python, etc., with different approaches.

Longest Substring Without Repeating Characters LeetCode Solution

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.

• C++ Solution
• Java Solution
• JavaScript Solution
• Python Solution

Longest Substring Without Repeating Characters Leetcode Solution C++ ->

class Solution {
public:
    int lengthOfLongestSubstring(string s) {
        int n = int(s.length()), res = 0;
        unordered_map<char, int> mp;

        for (int j = 0, i = 0; j < n; j++){
            if(mp[s[j]] > 0) {
                i = max(mp[s[j]], i);
            }
            res = max(res, j - i + 1);
            mp[s[j]] = j + 1;
        }
        return res;
    }
};
Code language: C++ (cpp)

Longest Substring Without Repeating Characters Leetcode Solution Java ->

public class Solution {
    public int lengthOfLongestSubstring(String s) {
        int n = s.length(), ans = 0;
        Map<Character, Integer> map = new HashMap<>(); // current index of character
        // try to extend the range [i, j]
        for (int j = 0, i = 0; j < n; j++) {
            if (map.containsKey(s.charAt(j))) {
                i = Math.max(map.get(s.charAt(j)), i);
            }
            ans = Math.max(ans, j - i + 1);
            map.put(s.charAt(j), j + 1);
        }
        return ans;
    }
}
Code language: Java (java)

Longest Substring Without Repeating Characters Leetcode Solution JavaScript ->

var lengthOfLongestSubstring = function(s) {
  var sLen = s.length,
    maxLen = 0,
    maxStr = '',
    tmpStr,
    posIndex,
    i;

  for( i = 0 ; i < sLen; i++ ){
    tmpStr = s[i];
    posIndex = maxStr.indexOf(tmpStr);

    if(posIndex > -1){
      maxStr = maxStr.substring(posIndex + 1);
    }
    maxStr += tmpStr;
    maxLen = Math.max(maxLen, maxStr.length);
  }
  return maxLen;
};
Code language: JavaScript (javascript)

Longest Substring Without Repeating Characters Leetcode Solution Python ->

class Solution:
    def lengthOfLongestSubstring(self, s: str) -> int:
        n = len(s)
        ans = 0
        # mp stores the current index of a character
        mp = {}

        i = 0
        # try to extend the range [i, j]
        for j in range(n):
            if s[j] in mp:
                i = max(mp[s[j]], i)

            ans = max(ans, j - i + 1)
            mp[s[j]] = j + 1

        return ans
Code language: Python (python)