002_fibonacci

Fibonacci

• 🧩 Problem link: Leetcode
• 🚦 Difficulty: 🟢 Easy

🕒 Time and Space Complexity

• Time: O(2^n)
• Space: O(n)

✅ Solution 01 - Recursive

// Recursive implementation to calculate the n-th Fibonacci number
int fibonacci(int n)
{
    // Base case: n = 0 or 1
    if (n <= 1)
    {
        return n;
    }
    // Recursive case: fib(n) = fib(n - 1) + fib(n - 2)
    return fibonacci(n - 1) + fibonacci(n - 2);
}

✅ Solution 02 - Iterative

int fibonacci(int n)
{
    if (n <= 0)
        return;

    int a = 0, b = 1;

    for (int i = 0; i < n; i++)
    {
        cout << a << " ";
        long long nextTerm = a + b;
        a = b;
        b = nextTerm;
    }
}

🕒 Time and Space Complexity

• Time: O(n)
• Space: O(n)