How to use a for loop to find Armstrong numbers in C++?

A narcissistic number is an n-digit number that is equal to the sum of each digit raised to the power of n. For example, 153 is a narcissistic number because 1^3 + 5^3 + 3^3 = 153.

Here is an example code using a for loop to find Armstrong numbers.

#include <iostream>
#include <cmath>

int main() {
    int num, n, digit, sum;
    
    for(num = 100; num < 1000; num++) {
        n = 0;
        sum = 0;
        int temp = num;
        
        // 计算num的位数
        while(temp != 0) {
            temp /= 10;
            n++;
        }
        
        temp = num;
        
        // 求每个位上的数的n次幂之和
        while(temp != 0) {
            digit = temp % 10;
            sum += pow(digit, n);
            temp /= 10;
        }
        
        // 判断是否是水仙花数并输出
        if(num == sum) {
            std::cout << num << " ";
        }
    }
    
    return 0;
}

This code will print all three-digit Armstrong numbers, such as 153, 370, 371, 407. You can modify the range and number of digits in the loop to calculate Armstrong numbers with different digits as needed.