How to Get Sum of Series 1-2+3-4+…. +n in C Program

It is easy to get sum of series 1 – 2 + 3 – 4 + . . . + n in C program. In this tutorial, I’ll show you how to do it in easy way in C program. Here is a simple code for it:

#include <stdio.h>

int main()
{
int n,i;
int s=0;


printf("Enter the value of n of the series: ");
scanf("%d",&n);


printf("Sum of the series: ");


for (i =1; i <= n; i++)
{
s=s+i*pow(-1,i+1);
if(i>=n)
printf("%d = %d ",i,s);
else
if(i%2==0)
printf("%d + ",i);
else
printf("%d - ",i);
}


return 0;
}

Output:

Enter the value of n of the series: 10
Sum of the series: 1 - 2 + 3 - 4 + 5 - 6 + 7 - 8 + 9 - 10 = -5


In above code, I have tried to show number, plus sign, result and in a word equation  by iterating from 2 to n using for loop by incrementing 2 and as well as summing up the series in the iteration.

In this tutorial, I have shown how to get sum of series 1 – 2 + 3 – 4 + . . . + n in C Program. Hope you have enjoyed the tutorial. If you want to get updated, like the facebook page http://www.facebook.com/freetechtrainer and stay connected.