Longest Substring Without Repeating Characters LeetCode Solution Best & Easiest

Posted by admin February 15, 2023

In this post, we will solve the 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.

Longest Substring Without Repeating Characters LeetCode Solution

Problem solution in JavaScript programming:

function lengthOfLongestSubstring(s) {
  let maxLength = 0, start = 0, end = 0;
  const charIndexMap = {};
  
  while (end < s.length) {
    const char = s[end];
    if (charIndexMap[char] >= start) {
      start = charIndexMap[char] + 1;
    }
    charIndexMap[char] = end;
    maxLength = Math.max(maxLength, end - start + 1);
    end++;
  }
  
  return maxLength;
}

Problem solution in Python programming:

def lengthOfLongestSubstring(self, s):
        max_length = 0
        start = 0
        char_index_map = {}

        for end in range(len(s)):
            char = s[end]
            if char in char_index_map and char_index_map[char] >= start:
                start = char_index_map[char] + 1
            char_index_map[char] = end
            max_length = max(max_length, end - start + 1)

        return max_length

Problem solution in C++ programming:

int lengthOfLongestSubstring(std::string s) {
    int maxLength = 0;
    int start = 0;
    std::unordered_map<char, int> charIndexMap;

    for (int end = 0; end < s.length(); end++) {
        char c = s[end];
        if (charIndexMap.count(c) && charIndexMap[c] >= start) {
            start = charIndexMap[c] + 1;
        }
        charIndexMap[c] = end;
        maxLength = std::max(maxLength, end - start + 1);
    }

    return maxLength;
}