findNarcissisticNumbersRange()

Step 1: Understand the Problem

In this step, we need to understand what's a Narcissistic number. A narcissistic number in a given number base b is a number that is the sum of its own digits each raised to the power of the number of digits. For example, 153 is narcissistic number, as 1^3 + 5^3 + 3^3 = 153.

So, to solve this problem we would construct a java function that takes in two integers which represent the starting and ending points of the range, and we would return all the narcissistic numbers within that range.

Step 2: Define the Function

Start by defining the java method, findNarcissisticNumbers, which will take two integers start and end as the range.

public static List<Integer> findNarcissisticNumbers(int start, int end) {

}

Step 3: iterate over the range

Now we're going to iterate over the range from start to end. We will check in each step if the number is a narcissistic number.

public static List<Integer> findNarcissisticNumbers(int start, int end) {
    List<Integer> narcNums = new ArrayList<>();
    for (int i = start; i <= end; i++){
    }
    return narcNums;
}

Step 4: Check if a number is a narcissistic number

To check if a given number is a narcissistic number, we will convert the number into a string to easily get the number of digits. Then we will iterate over each digit and raise it to the power of the total number of digits and check if the sum is equal to the number itself.

public static List<Integer> findNarcissisticNumbers(int start, int end) {
    List<Integer> narcNums = new ArrayList<>();
    for (int i = start; i <= end; i++){
        String num = Integer.toString(i);
        int sum = 0;
        int len = num.length();
        for (char c : num.toCharArray()){
            int digit = Character.getNumericValue(c);
            sum += Math.pow(digit, len);
        }
        if (sum == i)
            narcNums.add(i);
    }
    return narcNums;
}

Conclusion

That's it! We have now successfully programmed a function in java that finds all the narcissistic numbers in a given range. The function works by iterating over the range and checking if each number is a narcissistic number, by raising each digit to the power of the total number of digits and checking if the sum equals the original number.