diff --git a/136-single-number/single-number.cpp b/136-single-number/single-number.cpp
new file mode 100644
index 0000000..a91f56c
--- /dev/null
+++ b/136-single-number/single-number.cpp
@@ -0,0 +1,19 @@
+class Solution {
+public:
+    int singleNumber(vector<int>& nums) {
+        unordered_map<int,int> mp;
+        int x;
+        for(auto & x: nums)
+        {
+            mp[x]++;
+        }
+        for(auto & y: mp)
+        {
+        if(y.second == 1)
+            
+             return y.first;
+        }
+       return -1;
+        
+    }
+};
\ No newline at end of file