#include #include #include using namespace std; /* * The definition in the assignment is actually wrong! * This is the correct definition of Armstrong numbers: * "An n-digit number that is the sum of the nth powers of its digits is called an n-narcissistic number." * * UPDATE: For a more beautiful output I decided to include and . * Instead of directly printing the numbers in the main function, I save them and print them later. */ bool armstrong(int input) { int n = input; // the nth digit int result = 0; // we'll calculate the powers of the digits and add them up int r; // the remainder from the modulo operation <=> the value of the current digit int power = 0, summand; // for the power function // Count the digits to find the power. for (int i = input; i != 0; i /= 10) ++power; while (n != 0) { // Find the next digit. r = n % 10; // The pow()-function from the cmath library will calculate wrong results for integers. // Instead of using doubles I'll save memory and implement my own power function here. summand = r; for (int i = 1; i < power; ++i) summand *= r; // Add the n-th power of the given digit to the result. result += summand; n /= 10; } // Et voila. return (input == result) ? true : false; } int main() { // Getting input int range; cin >> range; // Finding the numbers vector numbers; for (int i = 0; i <= range; ++i) if (armstrong(i)) numbers.push_back(i); // Formatting stuff int width = 0; for (int i = numbers.back(); i != 0; i /= 10) ++width; // Ouput cout << "Armstrong numbers in the range from 0 to " << range << ":\n\n"; for (int n : numbers) cout << setw(width) << n << endl; return 0; }

Coding Challenge #2: Armstrong Numbers