Which of the following code snippets returns the factorial of a given number? (Hint: Factorial of 5 = 5! = 1 * 2 * 3 * 4 * 5 = 120)

Question

BlackTom AI · Accepted Answer

To begin, let's evaluate what a correct factorial function must do. It needs a base case that stops recursion (commonly when num reaches 1) and a recursive case that reduces the problem size by calling itself with num - 1, multiplying the result by the current num.
Option 1: The function computes the factorial but uses print instead of return in the recursive branch. This means it outputs the intermediate product but the function call itself returns None, which would fail to produce the expected factorial value for use in further expressions. The presence of print instead of return is a fundamental flaw for a factorial function.
Option 2: The else branch does return num * factorial(num) without decreasing the argument. This creates infinite recursion because the input to factorial never changes, so the base case is never reached. Consequently, this cannot compute a finite factorial and will eventually raise a recursion depth error.
Option 3: The function multiplies num by factorial(num - 1) but lacks a base case entirely. Without a termination condition, the recursion never stops (except in pathological cases) and will lead to a stack overflow or recursion depth limit, never returning a valid factorial value.
Option 4: This version provides a proper base case (if num == 1, return 1) and a correct recursive step (return num * factorial(num - 1)). With input 5, it would compute 5 * 4 * 3 * 2 * 1 = 120, matching the mathematical definition of 5!. This option aligns with the standard recursive factorial pattern and will yield the correct result for positive integers.
In summary, the first option misuses print, the second and third options lack proper base case logic or reduce the problem incorrectly, and the fourth option correctly implements both the base case and the recursive step needed to compute a factorial.

Which of the following code snippets returns the factorial of a given number? (Hint: Factorial of 5 = 5! = 1 * 2 * 3 * 4 * 5 = 120)单项选择题

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