Final solution

C++/Arithmetic Number.cpp

@@ -5,7 +5,7 @@ using namespace std;
 
 int inSequence(int a, int b, int c)
 {
-    if (c == 0)
+    if (c == 0 )
     {
         if (a != b)
         {

C++/Single Number.cpp

@@ -0,0 +1,27 @@
+#include<bits/stdc++.h>
+using namespace std;
+#define lld long long int 
+
+
+int singlenumber(int arr[],int n)
+{
+   int ans=0;//we will use the xor property stating that xors of 2 same numbers is 0
+   for(int i=0;i<n;i++)
+   {
+    ans=ans^arr[i];
+   }
+   return ans;
+
+
+
+
+
+}
+
+
+
+
+int main()
+{
+    return 0;
+}

C++/Sort an array of 0s, 1s and 2s.cpp

@@ -0,0 +1,61 @@
+#include<bits/stdc++.h>
+using namespace std;
+#define lld long long int 
+
+void sort012(int arr[],int n)
+{
+   int temp[3]={0};//we will apply count sort so its the storing array
+
+//traversing over the array and will increase the suitable index value
+   for(int i=0;i<n;i++)
+   {
+    if(arr[i]==1)
+    {
+       temp[1]++;
+    }
+    else if(arr[i]==0)
+    {
+        temp[0]++;
+    }
+    else
+    {
+        temp[2]++;
+    }
+   }
+   int i=0;
+   while(arr[0]>0&&i<n)
+   {
+      arr[i]=0;
+      arr[0]--;
+      i++;
+   }
+
+   while(arr[1]>0&&i<n)
+   {
+      arr[i]=1;
+      arr[1]--;
+      i++;
+   }
+
+   while(arr[2]>0&&i<n)
+   {
+      arr[i]=2;
+      arr[2]--;
+      i++;
+   }
+
+
+
+
+
+
+}
+
+
+
+
+
+int main()
+{
+    return 0;
+}