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      • C Recursion

      Recursion is when a function calls itself.

      1. Basic Recursion

      int factorial(int n) {
    if (n <= 1) {
        return 1;
    }
    return n * factorial(n - 1);
}

      2. Fibonacci Sequence

      int fibonacci(int n) {
    if (n <= 1) {
        return n;
    }
    return fibonacci(n - 1) + fibonacci(n - 2);
}

      3. Key Points

      • Base case is essential to prevent infinite recursion
      • Each recursive call uses stack space
      • Some problems are naturally recursive (tree traversal, factorial, etc.)

      4. Tail Recursion

      int factorial_tail(int n, int acc) {
    if (n <= 1) {
        return acc;
    }
    return factorial_tail(n - 1, n * acc);
}