Added armstrong number program.

Dynamic Programming/Armstrong Number.cpp

@@ -0,0 +1,20 @@
+//program to check whether a number is an armstrong number or not
+#include<iostream.h>
+#include<Math.h>
+int main()
+{
+  int n,k,d,s=0;
+  cout<<"Enter a number:";
+  cin>>n;
+  k=n;
+  while(k!=0)
+  {
+    d=k%10;
+    s+=(int)pow(d,3);
+    k/=10;
+  }
+  if(s==n)
+   cout<<n<<"is an armstrong number";
+  else
+   cout<<n<<"is not an armstrong number";
+}

Dynamic Programming/Armstrong Number.txt

@@ -0,0 +1,17 @@
+Armstrong number
+
+An armstrong number is a number whose sum of cube of digits is equal to the original number.
+
+Example: 153
+
+Here,
+  Sum of cube of digits= cube(1)+cube(5)+cube(3)
+                       = 1+125+27
+                       = 153
+  This is equal to the entered number. Hence, 153 is an armstrong number.
+
+Code:
+
+> In our code, we have extracted each digit of the number, found its cube and stored the sum of all such cubes in a variable. This sum has been compared in the end with the original number.
+
+> We have used a function 'pow' to find the cube of each digit. For its implementation, a header file 'Math.h' has been used.