[Add] solved solutions

cpp/CHEFDETE.cpp

@@ -0,0 +1,29 @@
+#include <iostream>
+
+using namespace std;
+
+void xu_ly(int n)
+{
+    bool mang[n + 1] = {0}, t, i;
+    for (i = 0; i < n; i++)
+    {
+        cin >> t;
+        mang[t] = 1;
+    }
+    for (i = 1; i <= n; i++)
+    {
+        if (!mang[i])
+        {
+            cout << i << " ";
+        }
+    }
+    //cout << '\b';
+}
+
+int main()
+{
+    int n;
+    cin >> n;
+    xu_ly(n);
+    return 0;
+}