diff --git a/Solved-Problems/Longest_Substring_Without_Repeating_Characters/Longest_Substring_Without_Repeating_Characters.cpp b/Solved-Problems/Longest_Substring_Without_Repeating_Characters/Longest_Substring_Without_Repeating_Characters.cpp
new file mode 100644
index 0000000..efc5b4b
--- /dev/null
+++ b/Solved-Problems/Longest_Substring_Without_Repeating_Characters/Longest_Substring_Without_Repeating_Characters.cpp
@@ -0,0 +1,63 @@
+#include <iostream>
+#include <string>
+#include <unordered_map>
+using namespace std;
+
+// Function to find the length of the longest substring without repeating
+// characters
+int lengthOfLongestSubstring(const string &s) {
+  unordered_map<char, int> charIndexMap;
+  int maxLength = 0;
+  int start = 0;
+
+  for (int end = 0; end < s.length(); end++) {
+    char currentChar = s[end];
+
+    // If the character is already in the map and is within the current window
+    if (charIndexMap.find(currentChar) != charIndexMap.end() &&
+        charIndexMap[currentChar] >= start) {
+      start = charIndexMap[currentChar] + 1;
+    }
+
+    // Update the last seen index of the current character
+    charIndexMap[currentChar] = end;
+
+    // Calculate the max length of substring
+    maxLength = max(maxLength, end - start + 1);
+  }
+  return maxLength;
+}
+
+int main() {
+  string input;
+  cout << "Enter a string: ";
+  cin >> input;
+
+  int result = lengthOfLongestSubstring(input);
+  cout
+      << "The length of the longest substring without repeating characters is: "
+      << result << endl;
+
+  return 0;
+}
+
+/*
+Example:
+Input: "abcabcbb"
+Explanation:
+- The longest substring without repeating characters is "abc", which has a
+length of 3.
+- As we iterate through the string:
+    - Start with "a" -> length 1
+    - Add "b" -> "ab" -> length 2
+    - Add "c" -> "abc" -> length 3
+    - "a" repeats, so move the start to the next character -> "bca" (length
+still 3)
+    - Continue until the end, with the longest substring remaining "abc".
+Output: 3
+
+Input: "bbbbb"
+Explanation:
+- The longest substring without repeating characters is "b", which has a length
+of 1. Output: 1
+*/