Prime Number using Recursion
Detailed guide and Python implementation for the 'Prime Number using Recursion' problem.
1. Concept Overview
The 'Prime Number using Recursion' problem is a key challenge in the Recursion section.
This implementation focuses on medium-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 Prime Number using Recursion.
4. Prerequisites
5. Step-by-Step Thinking
1. Understand the problem
Read the problem statement for Prime Number using Recursion 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_prime(n) that checks whether the given positive integer n is a prime number using recursion. The function should return True if n is prime and False otherwise. A prime number is a number greater than 1 that has no divisors other than 1 and itself.
- •1 <= n <= 10000
Examples
n = 7
True
7 is only divisible by 1 and 7, so it is prime.
n = 10
False
10 is divisible by 2 and 5, so it is not prime.
n = 1
False
1 is not considered a prime number by definition.
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_prime(n):
if n <= 1: return False
if n <= 3: return True
if n % 2 == 0 or n % 3 == 0: return False
def check(n, i):
if i * i > n: return True
if n % i == 0 or n % (i + 2) == 0: return False
return check(n, i + 6)
return check(n, 5)Brute Force Code (Spoiler Guarded)
Brute Force Code (Spoiler Guarded)
def is_prime(n, i=2):
if n <= 2:
return n == 2
if n % i == 0:
return False
if i * i > n:
return True
return is_prime(n, i + 1)Algorithm Pattern Checklist
When dealing with Recursion data patterns.
Core Prerequisites
Revision Key Notes
Common Mistakes & Pitfalls
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