Leetcode #1271: Hexspeak
In this guide, we solve Leetcode #1271 Hexspeak in Python and focus on the core idea that makes the solution efficient.
You will see the intuition, the step-by-step method, and a clean Python implementation you can use in interviews.
Problem Statement
A decimal number can be converted to its Hexspeak representation by first converting it to an uppercase hexadecimal string, then replacing all occurrences of the digit '0' with the letter 'O', and the digit '1' with the letter 'I'. Such a representation is valid if and only if it consists only of the letters in the set {'A', 'B', 'C', 'D', 'E', 'F', 'I', 'O'}.
Quick Facts
- Difficulty: Easy
- Premium: Yes
- Tags: Math, String
Intuition
There is a mathematical invariant or formula that directly leads to the result.
Using math avoids unnecessary loops and reduces complexity.
Approach
Derive the formula or update rule, then compute the answer directly.
Handle edge cases like overflow or zero carefully.
Steps:
- Identify the math relationship.
- Compute the result with a loop or formula.
- Handle edge cases.
Example
Input: num = "257"
Output: "IOI"
Explanation: 257 is 101 in hexadecimal.
Python Solution
class Solution:
def toHexspeak 🔒(self, num: str) -> str:
s = set('ABCDEFIO')
t = hex(int(num))[2:].upper().replace('0', 'O').replace('1', 'I')
return t if all(c in s for c in t) else 'ERROR'
Complexity
The time complexity is , where is the size of the decimal number represented by . The space complexity is O(1).
Edge Cases and Pitfalls
Watch for boundary values, empty inputs, and duplicate values where applicable. If the problem involves ordering or constraints, confirm the invariant is preserved at every step.
Summary
This Python solution focuses on the essential structure of the problem and keeps the implementation interview-friendly while meeting the constraints.