C, while adding number each run

Question

Hello fairly new at coding, i have this program which should add a number each time the program is run, it computes 1 + 2 + 3 +......(n - 1) + n and an if statement that compares the value to (n*(n+1))/2 and then displays a message if its the same or different.

#include <stdio.h>

int main(void)
{

  int value = 0, n_data_value, count = 0, second_value;

  printf("Enter a number\n");
  scanf("%lf", &n_data_value);

  while (count < 10) {
   value = (1 + value) + (n_data_value - 1) + n_data_value;
   printf("%f\n", value);
   second_value = (n_data_value * (n_data_value + 1))/2;
   printf("The number is %f\n", value);
   count = count + 1;

   if(value = second_value){
     printf("value = %f and second_value = %f", value, second_value);
   }
  } 
 return 0;
}

When i run it i just get this

Enter a number 3

0.000000

The number is 0.000000

0.000000

The number is 0.000000

0.000000

The number is 0.000000

0.000000

The number is 0.000000

0.000000

The number is 0.000000

0.000000

The number is 0.000000

0.000000

The number is 0.000000

0.000000

The number is 0.000000

0.000000

The number is 0.000000

0.000000

The number is 0.000000

When you get your program working and fix your loop logic and maths, you'll find a disparity between the formula and your looped value after N=65535. See stackoverflow.com/questions/12923523/… — paddy
– paddy, Commented Oct 29, 2012 at 13:26

Klas Lindbäck · Accepted Answer · 2012-10-29 11:43:13Z

1

Use %d with int variables in scanf/printf.

%lf is for double values.

answered Oct 29, 2012 at 11:43

Klas Lindbäck

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Comments

simonc · Accepted Answer · 2012-10-29 11:51:00Z

1

The test for value matching second_value is also wrong. Use == to test for equality

i.e. change

if(value = second_value){

to

if(value == second_value){

Note that compiling with warnings enabled (-Wall for gcc, /W4 for msvc) would have flagged this up for you.

edited Oct 29, 2012 at 11:51

answered Oct 29, 2012 at 11:45

simonc

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2 Comments

Winkz Over a year ago

Hmm how do i enable warnings in the compiler? just add -wall or? :)

simonc Over a year ago

If you're compiling from the command line, add -Wall for gcc or /W4 for msvc. If you're using an IDE, there will be a build settings dialog which accepts compiler flags

Joze · Accepted Answer · 2012-10-29 13:20:43Z

If you want to do it more than 1 time : just add something like that :

#include <stdio.h>

int main(void)
{

   int value = 0, n_data_value, count = 1, second_value;
   char char_quit='';

   do //Infinite loop
   {

      printf("Enter a number\n");
      scanf("%d", &n_data_value);

      while (count <= n_data_value) {//while loop to calculate 1+2+3+...+n
        value = value + count;
        count = count + 1;
      }
     second_value = (n_data_value * (n_data_value + 1))/2;//calculates n(n+1)/2
     printf("The number is %d\n", second_value);

     if(value == second_value)//compares value
     {
        printf("value = %d and second_value = %d", value, second_value);
     } 

     //Ask to continue ?
     printf("Do you want to continue ? Y/N \n"); //Y or any other key will force to continue the program
     scanf("%c", &char_quit );

  }while (char_quit == 'n' || char_quit == 'N');

  return 0;
}

You could naturally use something like : while(1) insteand of the "do while" if you want an infinite loop.

Bhavik Shah · Accepted Answer · 2012-10-29 11:50:47Z

0

I think you just need this

#include <stdio.h>

int main(void)
{

  int value = 0, n_data_value, count = 1, second_value;

  printf("Enter a number\n");
  scanf("%d", &n_data_value);

  while (count <= n_data_value) {//while loop to calculate 1+2+3+...+n
   value = value + count;
   count = count + 1;
  }
  second_value = (n_data_value * (n_data_value + 1))/2;//calculates n(n+1)/2
  printf("The number is %d\n", second_value);

 if(value == second_value){//compares value
     printf("value = %d and second_value = %d", value, second_value);
   } 
 return 0;
}

answered Oct 29, 2012 at 11:50

Bhavik Shah

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1 Comment

Winkz Over a year ago

Yes that works, but what if i wanted to run the program more times? :)

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