Question

How to calculate the sum of first N natural numbers in C

Answer 1

#include <stdio.h> 

// 1 + 2 + 3 + 4 + ... + N

int main(void)
{
    int n = 10, sum = 0;
 
    while (n > 0)
    {
        sum += n;
        n--;
    }
         
    printf("The sum is: %d\n", sum);
       
    return 0;
}
   
           
/*
run:
        
The sum is: 55

*/

 

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Answer 2

#include <stdio.h> 

// 1 + 2 + 3 + 4 + ... + N

int main(void)
{
    int n = 10, sum = 0;
 
    sum = n / 2 * (n + 1);
         
    printf("The sum is: %d\n", sum);
       
    return 0;
}
   
           
/*
run:
        
The sum is: 55

*/

 

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