Recursion vs iteration

Both recursion and iteration can solve repetitive problems. Choose based on clarity and performance constraints.

Aspect	Recursion	Iteration
Memory	Uses stack (each call adds a frame)	Uses fixed memory (loop variables)
Performance	Overhead of function calls	Generally faster (no call overhead)
Risk	Stack overflow for deep recursion	No stack overflow
Readability	Elegant for tree‑like problems (e.g., file system, divide & conquer)	Better for simple, linear problems
Code size	Often shorter	Usually longer

Example – factorial (recursion vs iteration):

// Recursive
int factRec(int n) {
    if (n <= 1) return 1;
    return n * factRec(n - 1);
}

// Iterative
int factIter(int n) {
    int result = 1;
    for (int i = 2; i <= n; i++) {
        result *= i;
    }
    return result;
}

When to use recursion:

• Tree/graph traversal
• Backtracking (e.g., maze solving, N‑Queens)
• Divide and conquer (merge sort, quick sort)
• Problems with recursive definition (Fibonacci, factorial)

When to use iteration:

• Simple loops over arrays/collections
• Performance‑critical code
• When depth is large or unknown

Hybrid approach: Use recursion for clarity, but convert to iteration with explicit stack if needed for performance.