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+# Length of the Longest Substring without Repeating Characters
+
+Here we will see a program to find the length of Longest substring without repeating characters.  
+
+## Explanation
+In this program we are using the concept of Window sliding i.e. Whenever we see repetition, we remove the previous occurrence and slide the window.  
+A loop is runniig from i=0 to n=sizeof(str).  
+In side this loop one more loop is running from j=i till n.  
+We define vector with all the value as false and keep it makin true for the characters that are visited once in the loop.
+
+## Code
+``` cpp
+#include <bits/stdc++.h>
+using namespace std;
+ 
+int Substtr(string str)
+{
+    int n = str.size();
+    int result = 0; 
+ 
+    for (int i = 0; i < n; i++) {
+         
+        vector<bool> visited(256);  
+ 
+        for (int j = i; j < n; j++) {
+
+            if (visited[str[j]] == true)  // If current character is visited
+                  break;                         // Break the loop
+                       
+            else {                          // Else update the result if
+                res = max(res, j - i + 1);  // this window is larger, and mark
+                visited[str[j]] = true;       // current character as visited.
+            }
+        }
+        
+        visited[str[i]] = false;  // Remove the first character of previous window
+    }
+    return result;
+}
+ 
+int main()
+{
+    string str = "girlscriptwinterofcontributing";
+    cout << "The string used is " << str << endl;
+    int length =Substtr(str);
+    cout << "The length of the longest non-repeating "
+            "character substring is "
+         << length;
+    return 0;
+}
+
+```
+## Time and Space Complexity
+**Time Complexity**: O(n^2)  
+**Space Complexity**:O(n)
+
+## Input/Output
+**Input**: s = "abcabcbb"  
+**Output**: 3  
+**Explanation**: The answer is "abc", with the length of 3.