C Exercises: Find the sum of specified series

Last update on October 24 2025 12:09:27 (UTC/GMT +8 hours)

5. Series Sum Using Function Variants

Write a program in C to find the sum of the series 1!/1+2!/2+3!/3+4!/4+5!/5 using the function.

Pictorial Presentation:

C Exercises: Find the sum of specified series

Sample Solution:

C Code:

#include <stdio.h>

int fact(int);
void main()
{
    int sum;
    sum=fact(1)/1+fact(2)/2+fact(3)/3+fact(4)/4+fact(5)/5;
	printf("\n\n Function : find the sum of 1!/1+2!/2+3!/3+4!/4+5!/5 :\n");
	printf("----------------------------------------------------------\n");    
    printf("The sum of the series is : %d\n\n",sum);
}

int fact(int n)
    {
        int num=0,f=1;
        while(num<=n-1)
        {
            f =f+f*num;
            num++;
        }
    return f;
    }

Sample Output:

 Function : find the sum of 1!/1+2!/2+3!/3+4!/4+5!/5 :
----------------------------------------------------------
The sum of the series is : 34

Explanation:

int fact(int n) {
  int num = 0, f = 1;
  while (num <= n - 1) {
    f = f + f * num;
    num++;
  }
  return f;
}

In the above code the function 'fact' takes a single argument 'n' (type int). It computes the factorial of the input number 'n' using a while loop. The function initializes two local integer variables, 'num' and 'f', to 0 and 1 respectively. It then enters a loop that iterates n-1 times, incrementing num by 1 in each iteration. In each iteration of the loop, the value of f is updated by multiplying it with num incremented by 1. This computes the factorial of 'n' and returns the result.

Time complexity and space complexity:

The time complexity of the function 'fact' is O(n), where 'n' is the input number, as the loop in the function iterates n-1 times.

The space complexity of this function is O(1), as it only uses a fixed amount of memory to store the two integer variables 'num' and 'f'.

Flowchart:

Flowchart: Find the sum of specified series

For more Practice: Solve these Related Problems:

Write a C program to calculate the sum of the series n!/n for n from 1 to a given number using a dedicated function.
Write a C program to compute the sum of a modified series where each term is n! divided by (n+1) using a function.
Write a C program that uses recursion within a function to calculate each term of the series and sums them.
Write a C program to compute the series sum 1/1! + 2/2! + 3/3! + ... and compare the result with the expected mathematical constant.

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