🧮 Day 17

Author: AkashRajpurohit

README.md

@@ -28,6 +28,7 @@
 
 1. [Rotate Array](https://leetcode.com/explore/challenge/card/october-leetcoding-challenge/561/week-3-october-15th-october-21st/3496/) ➡️ [CPP Solution](Week3/rotate.cpp)
 2. [Search a 2D Matrix](https://leetcode.com/explore/challenge/card/october-leetcoding-challenge/561/week-3-october-15th-october-21st/3497/) ➡️ [CPP Solution](Week3/searchMatrix.cpp)
+3. [Repeated DNA Sequences](https://leetcode.com/explore/challenge/card/october-leetcoding-challenge/561/week-3-october-15th-october-21st/3498/) ➡️ [CPP Solution](Week3/findRepeatedDnaSequences.cpp)
 
 ## Week 4 🚧
 

Week3/findRepeatedDnaSequences.cpp

@@ -0,0 +1,21 @@
+class Solution {
+public:
+    vector<string> findRepeatedDnaSequences(string s) {
+        unordered_map<string, int> seen;
+        int n = s.size();
+        vector<string> res;
+        
+        if(n < 10) return {};
+        
+        for(int i = 0; i + 10 <= n; ++i) {
+            string sub = s.substr(i, 10);
+            seen[sub]++;
+            
+            if(seen[sub] == 2) {
+                res.push_back(sub);
+            }
+        }
+        
+        return res;
+    }
+};