[C++] Add solution to Quick Brown Fox

Solutions/Quick Brown Fox/quickbrownfox.cpp

@@ -0,0 +1,27 @@
+#include <iostream>
+#include <string>
+
+using namespace std;
+
+int main() {
+    int n;
+    cin >> n;
+    while(n--) {
+        int freq[26] = { 0 };
+        string input;
+        getline(cin >> ws, input);
+        for(char letter : input) {
+            if(!isalpha(letter)) continue;
+            freq[tolower(letter) - 'a']++;
+        }
+        string missing = "";
+        for(int i = 0; i < 26; ++i) {
+            if (freq[i] == 0) {
+                missing += 'a' + i;
+            }
+        }
+        if(missing != "") cout << "missing " << missing << "\n";
+        else cout << "pangram" << "\n";
+    }
+    return 0;
+}