Скачать или смотреть LeetCode 509 Fibonacci Number in Python | Easy Coding Tutorial for Beginners

Solve LeetCode 509 "Fibonacci Number" in Python with this beginner-friendly coding tutorial! This problem asks you to find the nth Fibonacci number, where F(0) = 0, F(1) = 1, and F(n) = F(n-1) + F(n-2) for n {greater than} 1 (e.g., n = 4 returns 3). We’ll start with a recursive solution, then optimize it using dynamic programming to avoid redundant calculations. Perfect for Python learners, coding beginners, or anyone prepping for coding interviews!

🔍 *What You'll Learn:*
Understanding LeetCode 509’s requirements
Implementing a recursive Fibonacci solution in Python
Optimizing with dynamic programming (iterative approach)
Testing with example cases

💻 *Code Used in This Video:*
class Solution(object):
def fib(self, n):
"""
:type n: int
:rtype: int
"""
return n if n {less than} 2 else self.fib(n - 1) + self.fib(n-2)

Test cases
solution = Solution()

Test case 1: Base case
print(solution.fib(2)) # Output: 1
F(2) = F(1) + F(0) = 1 + 0 = 1

Test case 2: Larger number
print(solution.fib(4)) # Output: 3
F(4) = F(3) + F(2) = (F(2) + F(1)) + (F(1) + F(0)) = (1 + 1) + (1 + 0) = 3

Test case 3: Zero
print(solution.fib(0)) # Output: 0
F(0) = 0

Test case 4: One
print(solution.fib(1)) # Output: 1
F(1) = 1

Optimized iterative solution
class SolutionOptimized(object):
def fib(self, n):
"""
:type n: int
:rtype: int
"""
if n {less than} 2:
return n
a, b = 0, 1
for _ in range(2, n + 1):
a, b = b, a + b
return b

solution_opt = SolutionOptimized()
print("\nOptimized solution:")
print(solution_opt.fib(4)) # Output: 3
print(solution_opt.fib(0)) # Output: 0

🌟 *Why Solve LeetCode 509?*
This problem is a great introduction to recursion and dynamic programming in Python, a common topic in coding interviews! The recursive solution has a time complexity of O(2^n) due to redundant calculations, but the optimized iterative solution reduces it to O(n) with O(1) space complexity. Master this, and you’ll be ready for more advanced LeetCode challenges!

📚 *Who’s This For?*
Python beginners learning coding
Coding enthusiasts tackling LeetCode problems
Developers prepping for technical interviews

👍 Like, subscribe, and comment: What LeetCode problem should we solve next? Next up: More LeetCode dynamic programming problems—stay tuned!

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