Question

Display the output:
Number Factorial
1 1
2 2
3 6
4 24
5 120
pplx can some 1 write the code 4 me in C++

Answer 1

How far did you get with it and what gave you trouble?

Answer 2

@e.mccormick non

Answer 3

Well, why are you having problems making code to do this?

Answer 4

cox i missed the class i was ill that day

Answer 5

Well, what was the class on? Which aspect of C++? Loops? Recursion?

Answer 6

i think so it was on loops

Answer 7

OK. First off, do you know what a factorial is?

Answer 8

u have to display this out put on the screen
yup i know that 1! is 1 5! is 1.2.3.4.5

Answer 9

@e.mccormick plx help me

Answer 10

Good, good. OK. So, the idea of the loop os to do the repetitive work.

As you say there, the 5! is 1 times 2 times 3 times 4 times 5. But, what if your program is given some input x. Then how to tell the program to do x! as an operation. That is where the loop comes in. It does the repetitive work.

Answer 11

i dnt know that
thats what i am asking

Answer 12

There are two basic types of loops. One is the for loop, which does things for a specific set of items or number of times. The other is the while loop, which does things while something is true. There are some variants, but you can think about them as basically being those two things.

Answer 13

ahan right

Answer 14

This is an overview of loops:
http://www.tutorialspoint.com/cplusplus/cpp_loop_types.htm

But down a bit you can see they have the for loop in the loop type list:
http://www.tutorialspoint.com/cplusplus/cpp_for_loop.htm

At the bottom of that page there is this example:
```
#include <iostream>
using namespace std;

int main ()
{
// for loop execution
for( int a = 10; a < 20; a = a + 1 )
{
cout << "value of a: " << a << endl;
}

return 0;
}
```

Then they show the output as this:
value of a: 10
value of a: 11
value of a: 12
value of a: 13
value of a: 14
value of a: 15
value of a: 16
value of a: 17
value of a: 18
value of a: 19

As you can see, it started with 10 then counted to 19. This is all controled by the for statment:
for( int a = 10; a < 20; a = a + 1 )

for( ) is telling the compiler it is a for loop.

int a = 10; is the initial state. It makes the variable a as an integer type and sets it to 10.

a < 20; This is the condition part. It means "While a is less than 20, do this loop".

a = a + 1 Is what it does at the end of each pass of the loop.

So it starts with 10. Prints it as 10, set it to 11. 11 is less than 20 so it goes again. It keeps doing this until it hits 20, then the loop stops and it never prints 20.

That is one important concept. Where it starts and stops and why:

Answer 15

ahan

Answer 16

because you want to do a factorial you will want something in the loop to do the work, simple multiplication, but you will also want something outside the loop to store the result.

See, when you do that variable in the loop, the scope is in the loop. Once the loop ends, the variable goes away.

So, if I did this:

```
#include <iostream>
using namespace std;

int main ()
{
// for loop execution
for( int a = 10; a < 20; a = a + 1 )
{
cout << "value of a: " << a << endl;
}
cout << "value of a: " << a << endl;
return 0;
}
```

See the second cout << "value of a: " << a << endl;? It is outside the loop! So that would give an error because a is not declared outside the loop!

Answer 17

But lets say I did this:

```
#include <iostream>
using namespace std;

int main ()
{
int b = 0;
// for loop execution
for( int a = 10; a < 20; a = a + 1 )
{
cout << "value of a: " << a << endl;
b+=a;
}
cout << "sum of all a values: " << b << endl;
return 0;
}
```
Now I am countin a inside the loop and adding a to b inside the loop. Then, after the loop is done, I print out the sum I made. This would work!

This is also the foundation of how you want to do your factorial.

Answer 18

ahan

Answer 19

So, can you see how you could multiply using something like that?

Answer 20

yup right

Answer 21

Well, give it a try and see what you get. Just one hint. I did my outside variable as b=0 because I was doing addition. Starting with 0 for addition is important because it does not change the result. But you are doing multiplication! So your factorial saving variable must start as 1 so that it does not change the end result.

Answer 22

thnk u

Answer 23

And if you have trouble, post the code here. Just put a ``` above and below the code block. That is how I did the code highlighting. (It is the one with the ~ on the same key.) If you don't, it can't be copied or easily read...

Answer 24

its not working for factorilal

Answer 25

post your code...

Answer 26

Yes, we need to see what you did and how you are deciding what numbers.

Personally, I would use a count down loop so that it starts with the number, multiplies it into the factorial, counts down by 1, and keeps repeating while the value is > 1.