250+ TOP MCQs on Factorial using Recursion and Answers

Data Structure Multiple Choice Questions on “Factorial using Recursion”.

1. In general, which of the following methods isn’t used to find the factorial of a number?
a) Recursion
b) Iteration
c) Dynamic programming
d) Non iterative / recursive

Answer: d
Clarification: In general we use recursion, iteration and dynamic programming to find the factorial of a number. We can also implement without using iterative / recursive method by using tgammal() method. Most of us never use it generally.

2. Which of the following recursive formula can be used to find the factorial of a number?
a) fact(n) = n * fact(n)
b) fact(n) = n * fact(n+1)
c) fact(n) = n * fact(n-1)
d) fact(n) = n * fact(1)

Answer: c
Clarification: fact(n) = n * fact(n – 1) can be used to find the factorial of a number.

3. Consider the following iterative implementation to find the factorial of a number. Which of the lines should be inserted to complete the below code?

int main()
{
    int n = 6, i;
    int fact = 1;
    for(i=1;i<=n;i++)
      _________;
    printf("%d",fact);
    return 0;
}

a) fact = fact + i
b) fact = fact * i
c) i = i * fact
d) i = i + fact
Answer: b
Clarification: The line “fact = fact * i” should be inserted to complete the above code.

4. Consider the following recursive implementation to find the factorial of a number. Which of the lines should be inserted to complete the below code?

int fact(int n)
{
     if(_________)
        return 1;
     return n * fact(n - 1);
}
int main()
{
      int n = 5;
      int ans = fact(n);
      printf("%d",ans);
      return 0;
}

a) n = 0
b) n != 0
c) n == 0
d) n == 1

Answer: c
Clarification: The line “n == 0” should be inserted to complete the above code.
Note: “n == 1” cannot be used because it does not take care of the case when n = 0, i.e when we want to find the factorial of 0.

5. The time complexity of the following recursive implementation to find the factorial of a number is ________

int fact(int n)
{
     if(_________)
        return 1;
     return n * fact(n - 1);
}
int main()
{
      int n = 5;
      int ans = fact(n);
      printf("%d",ans);
      return 0;
}

a) O(1)
b) O(n)
c) O(n²)
d) O(n³)

Answer: b
Clarification: The time complexity of the above recursive implementation to find the factorial of a number is O(n).

6. What is the space complexity of the following recursive implementation to find the factorial of a number?

int fact(int n)
{
     if(_________)
        return 1;
     return n * fact(n - 1);
}
int main()
{
      int n = 5;
      int ans = fact(n);
      printf("%d",ans);
      return 0;
}

a) O(1)
b) O(n)
c) O(n²)
d) O(n³)
View Answer

Answer: a
Clarification: The space complexity of the above recursive implementation to find the factorial of a number is O(1).

7. Consider the following recursive implementation to find the factorial of a number. Which of the lines is the base case?

int fact(int n)
{
     if(n == 0)
        return 1;
     return n * fact(n - 1);
}
int main()
{
      int n = 5;
      int ans = fact(n);
      printf("%d",ans);
      return 0;
}

a) return 1
b) return n * fact(n-1)
c) if(n == 0)
d) if(n == 1)
View Answer

Answer: c
Clarification: The line “if(n == 0)” is the base case.

8. What is the output of the following code?

int fact(int n)
{
      if(n == 0)
        return 1;
      return n * fact(n - 1);
}
int main()
{
      int n = 0;
      int ans = fact(n);
      printf("%d",ans);
      return 0;
}

a) 0
b) 1
c) 2
d) 3
View Answer

Answer: b
Clarification: The program prints 0!, which is 1.

9. What is the output of the following code?

int fact(int n)
{
      if(n == 0)
        return 1;
      return n * fact(n - 1);
}
int main()
{
      int n = 1;
      int ans = fact(n);
      printf("%d",ans);
      return 0;
}

a) 0
b) 1
c) 2
d) 3
View Answer

Answer: b
Clarification: The program prints 1!, which is 1.

10. How many times will the function fact() be called when the following code is executed?

int fact(int n)
{
      if(n == 0)
        return 1;
      return n * fact(n - 1);
}
int main()
{
      int n = 5;
      int ans = fact(n);
      printf("%d",ans);
      return 0;
}

a) 4
b) 5
c) 6
d) 7
View Answer

Answer: c
Clarification: The fact() function will be called 6 times with the following arguments:
fact(5), fact(4), fact(3), fact(2), fact(1), fact(0).

11. What is the output of the following code?

int fact(int n)
{
      if(n == 0)
        return 1;
      return n * fact(n - 1);
}
int main()
{
      int n = 5;
      int ans = fact(n);
      printf("%d",ans);
      return 0;
}

a) 24
b) 120
c) 720
d) 1

Answer: b
Clarification: The function prints 5!, which is 120.

complete set of 1000+