Data Structure Questions and Answers – Sum of n Natural Numbers using Recursion

This set of Data Structure Multiple Choice Questions & Answers (MCQs) focuses on “Sum of n Natural Numbers using Recursion”.

1. Which of the following option is wrong about natural numbers?
a) Sum of first n natural numbers can be calculated by using Iteration method
b) Sum of first n natural numbers can be calculated by using Recursion method
c) Sum of first n natural numbers can be calculated by using Binomial coefficient method
d) No method is prescribed to calculate sum of first n natural number
View Answer

2. Which of the following gives the sum of the first n natural numbers?
a) nC2
b) (n-1)C2
c) (n+1)C2
d) (n+2)C2
View Answer

3. Consider the following iterative solution to find the sum of first n natural numbers:

#include<stdio.h>
int get_sum(int n)
{
      int sm = 0, i;
      for(i = 1; i <= n; i++)
        ________;
      return sm;
}
int main()
{
    int n = 10;
    int ans = get_sum(n);
    printf("%d",ans);
    return 0;
}

Which of the following lines completes the above code?
a) sm = i
b) sm += i
c) i = sm
d) i += sm
View Answer

4. What is the output of the following code?

#include<stdio.h>
int get_sum(int n)
{
      int sm, i;
      for(i = 1; i <= n; i++)
        sm += i;
      return sm;
}
int main()
{
    int n = 10;
    int ans = get_sum(n);
    printf("%d",ans);
    return 0;
}

a) 55
b) 45
c) 35
d) Depends on compiler
View Answer

5. What is the time complexity of the following iterative method used to find the sum of the first n natural numbers?

#include<stdio.h>
int get_sum(int n)
{
      int sm, i;
      for(i = 1; i <= n; i++)
        sm += i;
      return sm;
}
int main()
{
    int n = 10;
    int ans = get_sum(n);
    printf("%d",ans);
    return 0;
}

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

6. Consider the following code:

#include<stdio.h>
int recursive_sum(int n)
{
      if(n == 0)
        return 0;
      return ________;
}
int main()
{
    int n = 5;
    int ans = recursive_sum(n);
    printf("%d",ans);
    return 0;
}

Which of the following lines is the recurrence relation for the above code?
a) (n – 1) +recursive_sum(n)
b) n + recursive_sum(n)
c) n + recursive_sum(n – 1)
d) (n – 1) + recursive_sum(n – 1)
View Answer

7. Consider the following code:

#include<stdio.h>
int recursive_sum(int n)
{
      if(n == 0)
        return 0;
      return n + recursive_sum(n - 1);
}
int main()
{
     int n = 5;
     int ans = recursive_sum(n);
     printf("%d",ans);
     return 0;
}

Which of the following is the base case for the above recursive code?
a) if(n == 0)
b) return 0
c) return n + recursive_sum(n – 1)
d) if(n == 1)
View Answer

8. What is the time complexity of the following recursive implementation used to find the sum of the first n natural numbers?

#include<stdio.h>
int recursive_sum(int n)
{
      if(n == 0)
        return 0;
      return n + recursive_sum(n - 1);
}
int main()
{
     int n = 5;
     int ans = recursive_sum(n);
     printf("%d",ans);
     return 0;
}

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

9. Which of the following methods used to find the sum of first n natural numbers has the least time complexity?
a) Recursion
b) Iteration
c) Binomial coefficient
d) All have equal time complexity
View Answer

10. What is the output of the following code?

#include<stdio.h>
int recursive_sum(int n)
{
      if(n == 0)
        return 0;
      return n + recursive_sum(n - 1);
}
int main()
{
      int n = 5;
      int ans = recursive_sum(n);
      printf("%d",ans);
      return 0;
}

a) 10
b) 15
c) 21
d) 14
View Answer

11. How many times is the function recursive_sum() called when the following code is executed?

#include<stdio.h>
int recursive_sum(int n)
{
      if(n == 0)
        return 0;
      return n + recursive_sum(n - 1);
}
int main()
{
     int n = 5;
     int ans = recursive_sum(n);
     printf("%d",ans);
     return 0;
}

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

12. What is the output of the following code?

#include<stdio.h>
int recursive_sum(int n)
{
      if(n == 0)
        return 0;
      return n + recursive_sum(n - 1);
}
int main()
{
     int n = 0;
     int ans = recursive_sum(n);
     printf("%d",ans);
     return 0;
}

a) -1
b) 0
c) 1
d) runtime error
View Answer

13. What is the output of the following code?

#include<stdio.h>
int recursive_sum(int n)
{
      if(n == 0)
        return 0;
      return n + recursive_sum(n - 1);
}
int main()
{
     int n = -4;
     int ans = recursive_sum(n);
     printf("%d",ans);
     return 0;
}

a) 0
b) -10
c) 1
d) runtime error
View Answer

Sanfoundry Global Education & Learning Series – Data Structures & Algorithms.

To practice all areas of Data Structures & Algorithms, here is complete set of 1000+ Multiple Choice Questions and Answers.