Is Armstrong Number easy or hard?

Armstrong Number is considered an easy problem. It focuses on basic math logic and digit manipulation rather than advanced algorithms or complex data structures.

Armstrong Number Python/Java solution

Both Python and Java implementations follow the same logic: compute the digit count, iterate through digits, calculate digit^d, and compare the total with the original number. The algorithm runs in O(d) time and uses constant extra space.

How to solve Armstrong Number in O(n)?

Treat n as the input number and iterate through its digits. First compute the digit count d, then extract each digit using n % 10 and accumulate digit^d. Since each digit is processed once, the complexity is linear in the number of digits.

What is the best approach for Armstrong Number?

The digit extraction simulation approach is the most efficient. Count the digits, then repeatedly extract each digit using modulo and compute digit^d. This runs in O(d) time with O(1) space, where d is the number of digits.

Is Armstrong Number asked at Google/Amazon/Meta?

Armstrong number checks commonly appear in screening rounds and basic coding assessments rather than advanced onsite interviews. They test understanding of digit manipulation, loops, and mathematical operations.

What data structure is used in Armstrong Number?

No special data structure is required. The solution typically uses basic integer variables and arithmetic operations such as modulo and division to iterate through digits.

What is the time complexity of Armstrong Number?

The time complexity is O(d), where d is the number of digits in the number. Each digit is processed exactly once to compute digit^d and add it to the sum.

Description Hints 3 Solution Video 8:52

1134. Armstrong Number

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Given an integer n, return true if and only if it is an Armstrong number.

The k-digit number n is an Armstrong number if and only if the k^th power of each digit sums to n.

Example 1:

Input: n = 153
Output: true
Explanation: 153 is a 3-digit number, and 153 = 1³ + 5³ + 3³.

Example 2:

Input: n = 123
Output: false
Explanation: 123 is a 3-digit number, and 123 != 1³ + 2³ + 3³ = 36.

Constraints:

1 <= n <= 10⁸

Asked at 1 company

Amazon

Topics

Math

Hints open one at a time

Hint 1

Check if the given k-digit number equals the sum of the k-th power of it's digits.

Hint 2

How to compute the sum of the k-th power of the digits of a number ? Can you divide the number into digits using division and modulus operations ?

Hint 3

You can find the least significant digit of a number by taking it modulus 10. And you can remove it by dividing the number by 10 (integer division). Once you have a digit, you can raise it to the power of k and add it to the sum.

8:52

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