In this post, we are going to solve the** 3. Longest Substring Without Repeating Characters** problem of Leetcode. This problem **3. Longest Substring Without Repeating Characters** is a Leetcode

**medium**level problem. Let’s see code,

**.**

**3. Longest Substring Without Repeating Characters****Problem**

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.
```

**Constraints**

`0 <= s.length <= 5 * 10`

^{4}`s`

consists of English letters, digits, symbols and spaces.

Now, let’s see the code of **3. Longest Substring Without Repeating Characters** – Leetcode Solution.

**Longest Substring Without Repeating Characters** – Leetcode Solution

**Longest Substring Without Repeating Characters****3. Longest Substring Without Repeating Characters** – Solution in Java

**– Solution in Java**

**3. Longest Substring Without Repeating Characters**class Solution { public int lengthOfLongestSubstring(String s) { int n = s.length(), longest = 0; int[] nextIndex = new int[128]; for (int r=0, l=0; r<n; r++) { l = Math.max(nextIndex[s.charAt(r)], l); longest = Math.max(longest, r - l + 1); nextIndex[s.charAt(r)] = r + 1; } return longest; } }

**3. Longest Substring Without Repeating Characters** – Solution in C++

**C++**

**– Solution in****3. Longest Substring Without Repeating Characters**class Solution { public: int lengthOfLongestSubstring(string s) { int n = s.length(), longest = 0; vector<int> nextIndex(128); for (int r=0, l=0; r<n; r++) { l = max(nextIndex[s[r]], l); longest = max(longest, r - l + 1); nextIndex[s[r]] = r + 1; } return longest; } };

**3. Longest Substring Without Repeating Characters** **– Solution in **Python

**3. Longest Substring Without Repeating Characters****Python**

**– Solution in**class Solution: def lengthOfLongestSubstring(self, s): start = maxLength = 0 usedChar = {} for i in range(len(s)): if s[i] in usedChar and start <= usedChar[s[i]]: start = usedChar[s[i]] + 1 else: maxLength = max(maxLength, i - start + 1) usedChar[s[i]] = i return maxLength

**Note:** This problem **3. Longest Substring Without Repeating Characters** is generated by

**Leetcode**but the solution is provided by

**CodingBroz**. This tutorial is only for

**Educational**and

**Learning**purpose.