Armstrong number
Detailed guide and Python implementation for the 'Armstrong number' problem.
1. Concept Overview
The 'Armstrong number' problem is a key challenge in the Basics section.
This implementation focuses on easy-level logic in Python.
We prioritize technical accuracy and code readability in our provided solutions.
2. Real-World Applications
3. Visual Intuition
Visualizing the logic flow for Armstrong number.
4. Prerequisites
5. Step-by-Step Thinking
1. Understand the problem
Read the problem statement for Armstrong number carefully.
2. Formulate brute force
Draft a simple iterative solution.
3. Identify inefficiency
Look for redundant calculations.
4. Optimize search path
Use hashing or sorting to speed up the process.
5. Final Implementation
Clean up the code for production standards.
Problem Statement
Write a function is_armstrong(n) that takes a positive integer n and returns True if it is an Armstrong number, or False otherwise. An Armstrong number (narcissistic number) is a number that equals the sum of its own digits each raised to the power of the number of digits. For example, 153 has 3 digits and 1^3 + 5^3 + 3^3 = 153.
- •1 <= n <= 10^6
Examples
n = 153
True
153 has 3 digits. 1^3 + 5^3 + 3^3 = 1 + 125 + 27 = 153. So it is an Armstrong number.
n = 370
True
370 has 3 digits. 3^3 + 7^3 + 0^3 = 27 + 343 + 0 = 370.
n = 123
False
123 has 3 digits. 1^3 + 2^3 + 3^3 = 1 + 8 + 27 = 36, which is not 123.
Need a Hint?
Edge Cases to Watch
- Empty input structures
- Single element inputs
- Large numerical bounds
Ready to Solve?
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Interview Insights & Variations
Complexity Analysis Breakdown
Why Time: Directly evaluates all possibilities.
Why Space: Uses standard local memory.
Why Time: Optimized paths reduce total operations.
Why Space: May trade memory for speed.
Optimized Solution Python Code
Optimized Solution Python Code
def is_armstrong_opt(n: int) -> bool:
if n < 0: return False
digits, temp = [], n
while temp > 0:
digits.append(temp % 10)
temp //= 10
power = len(digits)
return n == sum(d ** power for d in digits)Brute Force Code (Spoiler Guarded)
Brute Force Code (Spoiler Guarded)
def is_armstrong_brute(n: int) -> bool:
s = str(n)
power = len(s)
total = sum(int(digit) ** power for digit in s)
return n == totalAlgorithm Pattern Checklist
When dealing with Basics data patterns.
Core Prerequisites
Revision Key Notes
Common Mistakes & Pitfalls
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