diff --git a/hard/day_12/solution.cpp b/hard/day_12/solution.cpp
index 8d3ad8d..328bf13 100644
--- a/hard/day_12/solution.cpp
+++ b/hard/day_12/solution.cpp
@@ -1 +1,32 @@
-//write your code here
\ No newline at end of file
+#include<bits/stdc++.h>
+using namespace std;
+
+int main() 
+{
+    int t;
+    cin >> t;
+    while(t--) 
+    {
+        int n;
+        cin >> n;
+        int arr[n];
+        for(int i=0; i<n; i++) 
+        {
+            cin >> arr[i];
+            if(i % 2 == 0) 
+            {
+                arr[i] = (arr[i] % 2 == 0) ? arr[i] : arr[i] + 1;
+            } 
+            else 
+            {
+                arr[i] = (arr[i] % 2 != 0) ? arr[i] : arr[i] + 1;
+            }
+        }
+
+        for(int i=0; i<n; i++) 
+        {
+            cout << arr[i] << " ";
+        }
+        cout << endl;
+    }
+}