Showing 153 is not an Armstrong number. (#680)

* Update Armstrong Number.cpp

* Update Armstrong Number.cpp

* Update Armstrong Number.cpp

* Update Armstrong Number.cpp

* Rename Armstrong Number.cpp to armstrong_number.cpp

* Update armstrong_number.cpp

Showing 153 as not an Armstrong number.

* Update armstrong_number.cpp

dynamic_programming/armstrong_number.cpp

@@ -0,0 +1,21 @@
+// Program to check whether a number is an armstrong number or not
+#include <iostream>
+
+using std::cout;
+using std::cin;
+
+int main() {
+  int n, k, d, s = 0;
+  cout << "Enter a number:";
+  cin >> n;
+  k = n;
+  while (k != 0) {
+    d = k % 10;
+    s += d * d * d;
+    k /= 10;
+  }
+  if (s == n)
+    cout << n << "is an armstrong number";
+  else
+    cout << n << "is not an armstrong number";
+}