Armstrong Number Python Solution with Tests

Tested Python solution for LeetCode 1134 with 32 pytest cases. Generate a practice environment with lcpy.

LeetCode 1134, Easy. Topics: Math. View on LeetCode.

Generate this problem as a practice environment: tested reference solution, 32 parametrized pytest cases, and a playground notebook:

lcpy gen -n 1134   # by problem number
lcpy gen -s armstrong_number   # by problem name

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Problem

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.

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Examples

Input: n = 153
Output: true
Explanation: 153 is a 3-digit number, and 153 = 1^3 + 5^3 + 3^3.

Input: n = 123
Output: false
Explanation: 123 is a 3-digit number, and 123 != 1^3 + 2^3 + 3^3 = 36.

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Constraints

• 1 <= n <= 10^8

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Solution

Reference implementation from solution.py on GitHub, full suite in test_solution.py:

class Solution:
    # Time: O(log n)
    # Space: O(1)
    def is_armstrong(self, n: int) -> bool:
        digits = str(n)
        k = len(digits)
        return sum(int(d) ** k for d in digits) == n

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Complexity

Time	Space
O(log n)	O(1)

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Tags

NeetCode All.