Create 0003-Longest-Substring-Without-Repeating-Characters.md

dsa-solutions/lc-solutions/0000-0099/0003-Longest-Substring-Without-Repeating-Characters.md

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+---
+id: longest-substrings-without-repeating-characters
+title: Longest Substring Without Repeating Characters (LeetCode)
+sidebar_label: 0003 - Longest Substring Without Repeating Characters
+tags:
+  - Hash table
+  - String
+  - Sliding Window
+description: "This is a solution to the Longest Substring Without Repeating Characters problem on LeetCode."
+---
+
+## Problem Description
+
+| Problem Statement                                             | Solution Link                                                                                                                                                             | LeetCode Profile                                    |
+| :------------------------------------------------------------ | :------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | :-------------------------------------------------- |
+| [Longest Substring Without Repeating Characters on LeetCode](https://leetcode.com/problems/longest-substring-without-repeating-characters/) | [Longest Substring Without Repeating Characters Solution on LeetCode](https://leetcode.com/problems/longest-substring-without-repeating-characters/solutions/5234730/solution/) | [Amruta Jayanti](https://leetcode.com/u/user7669cY/)|
+
+
+## Problem Description
+
+Given a string `s`, find the length of the  **longest substring**  without repeating characters.
+
+
+
+**Example 1:**
+
+```plaintext
+Input: s = "abcabcbb"
+Output: 3
+Explanation: The answer is "abc", with the length of 3.
+```
+
+**Example 2:**
+
+```plaintext
+Input: s = "bbbbb"
+Output: 1
+Explanation: The answer is "b", with the length of 1.
+```
+
+**Example 3:**
+
+```plaintext
+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 * 104`
+- `s` consists of English letters, digits, symbols and spaces.
+
+
+## Solution to the problem
+
+### Intuition and Approach
+This is a simple problem.Here try to maintain the unique characters and erase the repeating character.
+#### Implementation
+```python
+class Solution:
+    def lengthOfLongestSubstring(self, s: str) -> int:
+        n = len(s)
+        maxLength = 0
+        charSet = set()
+        left = 0
+
+        for right in range(n):
+            if s[right] not in charSet:
+                charSet.add(s[right])
+                maxLength = max(maxLength, right - left + 1)
+            else:
+                while s[right] in charSet:
+                    charSet.remove(s[left])
+                    left += 1
+                charSet.add(s[right])
+
+        return maxLength
+```
+Above is the implementation in Python.
+
+#### Complexity Analysis:
+- Time Complexity : $$O(n)$$ Here, n is the length of the substring
+- Space Complexity : $$O(min(n,m))$$ Here, m is the size of character set
+
+#### Codes in different languages:
+`CPP`:
+```cpp
+#include <vector>
+#include <string>
+#include <algorithm>
+
+class Solution {
+public:
+    int lengthOfLongestSubstring(string s) {
+        if (s.empty()) return 0;
+
+        int maxLength = 0;
+        std::vector<char> seen;
+
+        for (char c : s) {
+            auto it = std::find(seen.begin(), seen.end(), c);
+            if (it == seen.end()) {
+                seen.push_back(c);
+                maxLength = std::max(maxLength, static_cast<int>(seen.size()));
+            } else {
+                seen.erase(seen.begin(), it + 1); // Remove characters before the repeated character
+                seen.push_back(c);
+            }
+        }
+
+        return maxLength;
+    }
+};
+```
+
+`Java`:
+```java
+class Solution {
+    public int lengthOfLongestSubstring(String s) {
+        int n = s.length();
+        int maxLength = 0;
+        Set<Character> charSet = new HashSet<>();
+        int left = 0;
+
+        for (int right = 0; right < n; right++) {
+            if (!charSet.contains(s.charAt(right))) {
+                charSet.add(s.charAt(right));
+                maxLength = Math.max(maxLength, right - left + 1);
+            } else {
+                while (charSet.contains(s.charAt(right))) {
+                    charSet.remove(s.charAt(left));
+                    left++;
+                }
+                charSet.add(s.charAt(right));
+            }
+        }
+
+        return maxLength;
+    }
+}
+```