Looping Sums

[Sakinah]

Hi I am very very new to C++ i am trying to create a loop that reads 2 integers and addsall the intergers between. I am very very lost!
#include <iostream>
using namespace std;

int main()
{
int num1=10;
int num2=0;
int total;

while (num2<10)
{ total= num2+ 1;
total++;
}
system ("pause");
return 0;
}

[Savage]

Hi I am very very new to C++ i am trying to create a loop that reads 2 integers and addsall the intergers between. I am very very lost!
#include <iostream>
using namespace std;

int main()
{
int num1=10;
int num2=0;
int total;

while (num2<10)
{ total= num2+ 1;
total++;
}
system ("pause");
return 0;
}

Hi,this will start looping "when hell freezes over",because you are not increasing num2.

[JosAH]

So you want to sum m + (m+1) + (m+2) + ... + (n-2) + (n-1) + n?
Say for m=2 and n=6 you want to find 2+3+4+5+6?

There's a centuries old nice closed form formula available:

0+1+2 + ... + n= n*(n+1)/2

You don't want to count starting from 0, you want to count starting at m,
so the values 0, 1, 2, .. m-1 should be substracted again: that last sum,
using that same old formula again equals:

0+1+2+ ... + m-1 = (m-1)*m/2

So your sum for any m <= n (both nonnegative) equals:

n*(n+1)/2-(m-1)*m/2

We don't need no steenkin' loops ;-)

kind regards,

Jos

[Sakinah]

OK so I suck! I have only been doing this for 3 weeks.

[Sakinah]

ps thanks jos

[JosAH]

ps thanks jos

You're welcome of course. As you saw: there's no need for loops here. If your
assignment text tells you to use loops, simply add the numbers
m, (m+1), (m+2) ... (n-2), (n-1), n together; use a loop counter from m to n and
initialize a sum variable to zero before you start the loop.

kind regards,

Jos

[Sakinah]

ok this is exactly what my text says,...Write a C++ program with a loop structure that reads in 2 intergers, calculates the sum of all the intergers between thee 2 intergers (not including these 2 intergers) if any, and displays the final result. For example, if the 2 intergers ou read are -2 and 5, then your program should output 9 (=-1+0+1+2+3+4).


Sakinah :-)

[Ganon11]

OK, you can use a for...loop here if you'd like. The initial condition will set your index equal to num1 + 1, the end condition will be while the index is less than num2, and you will increment the index in each update. Inside the loop, add the index to the total.

[Savage]

ok this is exactly what my text says,...Write a C++ program with a loop structure that reads in 2 intergers, calculates the sum of all the intergers between thee 2 intergers (not including these 2 intergers) if any, and displays the final result. For example, if the 2 intergers ou read are -2 and 5, then your program should output 9 (=-1+0+1+2+3+4).


Sakinah :-)

First and first did you have to input numbers or are the numbers declared?

Find the diferance between those numbers:

5-(-2)=7,and lower it by two becasue you are not including limits of interval.

This will be 5,
so this is it:

<Code has been removed. Please review our FAQ Posting Guidelines>

Regards,Savage! !!

[Sakinah]

thanks a bunch :-)