diff --git a/lengthLongestSubstringWithoutRepeatingCharacters.cpp b/lengthLongestSubstringWithoutRepeatingCharacters.cpp
new file mode 100644
index 0000000..d1fac6d
--- /dev/null
+++ b/lengthLongestSubstringWithoutRepeatingCharacters.cpp
@@ -0,0 +1,39 @@
+
+#include <bits/stdc++.h>
+
+using namespace std;
+
+   int lengthOfLongestSubstring(string s) {
+         int j=0;
+         //if(s.size()==0)
+        // return 0;
+        map<int,int>mp;int ans=0;
+        for(int i=0;i<s.size();i++)
+        {
+            if(mp[s[i]] > 0)
+            {
+                while(mp[s[i]]!=0)
+                {
+                    mp[s[j]]--;
+                    j++;
+                }
+            }
+            
+            ans = max(ans,i-j+1);
+            mp[s[i]]++;
+        }
+        return ans;
+   }
+int main()
+{
+    int t;
+    cin>>t;
+    while(t--)
+    {
+       string s;
+       cin>>s;
+       int ans= lengthOfLongestSubstring(s);
+       cout<<ans<<endl;
+    }
+    return 0;
+}