Add cpplint to validate_filenames (#643)

* Add cpplint to validate_filenames

* Update and rename Happy_number.cpp to happy_number.cpp

* Update validate_new_filenames.yml

* pip install cpplint

* python3 -m pip install cpplint

* python3 -m pip install --useer cpplint

* python3 -m pip install --user cpplint

* Update validate_new_filenames.yml

* sudo python3 -m pip install cpplint

* sudo python3 -m pip install cpplint

* uses: actions/setup-python@v1

* Run cpplint first

* cpp_exts

* tuple

* cpplint_modified_files

Others/happy_number.cpp

@@ -0,0 +1,28 @@
+/* A happy number is a number whose sum of digits is calculated until the sum is a single digit,
+  and this sum turns out to be 1 */
+
+// Copyright 2019 TheAlgorithms contributors
+
+#include <iostream>
+
+int main() {
+  int n, k, s = 0, d;
+  std::cout << "Enter a number:";
+  std::cin >> n;
+  s = 0;
+  k = n;
+  while (k > 9) {
+    while (k != 0) {
+      d = k % 10;
+      s += d;
+      k /= 10;
+    }
+    k = s;
+    s = 0;
+  }
+  if (k == 1)
+    std::cout << n << " is a happy number" << std::endl;
+  else
+    std::cout << n << " is not a happy number" << std::endl;
+  return 0;
+}