How to write this as a forloop program?

[Milnk]

It goes like this, If the input is 5 it should output this.
1.2.3.4.5
2.4.6.8
3.6.9
4.8
5
Any idea how to do it? TYIA.

Edited: I have solved it myself Thanks a lot for the suggestions!

[jonnin]

if you look at it you just have
1-5 multiply each by 1
1-4, multiply by 2 each time
1-3, multiply by 3 each time
... so on

a pair of nested for loops gets that done. doing it with just one loop would be possible but rather odd looking.

[salem c]

> Any idea how to do it?
One step at a time.

Sooner or later, you'll be past the point where you can look at a problem and instantly write the answer in a single edit.

So you need to learn how to break the problem down into discrete steps which move toward the answer.

It's software, you can change any of it at any time by any amount.

#include <iostream>

int main()
{
    int n = 5; // input
    for(int row = 1 ; row <= n ; row++ ) {
        int row_length = n - row + 1;
        // int add = ?
        std::cout << "Row " << row 
                  << " has " << row_length << " numbers,"
                  << " and starts at " << row << "\n";
    }
}

Row 1 has 5 numbers, and starts at 1
Row 2 has 4 numbers, and starts at 2
Row 3 has 3 numbers, and starts at 3
Row 4 has 2 numbers, and starts at 4
Row 5 has 1 numbers, and starts at 5

Now you figure out some expression involving say row or n which tells you how much add.
When you've got that, the inner loop to print each row should be fairly obvious.

[Milnk]

Thanks, guys, fairly new to coding, and C++ is the one I started on. I'm had no trouble doing C++ until loop, really hard for me to understand. Are there any particular good guides I can use to understand the loop deeper?

[seeplus]

For an on-line C++ resource, have a look at

https://www.learncpp.com/

[jonnin]

ah, the single loop was not so bad with the extra variable. I was thinking of the one liner for loop when I said it was messy.

I don't know of a guide that will tell you the big picture so I will give you a short crack at it:

1) there are several kinds of loops, 4 types with variations on those.
2) the 4 kinds of loops are all interchangeable. The only reason there are 4 types is to make it easier to express the code.

the 4 types are: while, for, do-while, and ranged-for.
when to use them, in simple terms:

the while loop is used when you want to loop 0 or more times and all you need is one condition.
while(something < 10) for example. if something is 42, it will not enter the loop body at all, it will just skip it, because it is not less than 10.

the for loop is used when you need to control a variable as part of the activity. Your problem is a good example -- its a form of a multiplication table. Consider the multiples of 5, for example:
for(int i = 5; i <= 100; i+=5) //5,10,15,20,25,... 100. This is the most complex loop type: you can set up multiple variables and the action on the end does not *have* to just control the loop variables but can also do the work of the loop. This gets ugly and hackity looking in a hurry so use this power judiciously so that your code is still easy to read and maintain etc. You can put that information aside for now, but be aware of it because someday you will need to do this.

the do-while forces the loop body to execute once. It is a great tool for things like getting user input and making them enter the value again and again if they are not putting in valid responses.

do
{
 cout << "enter something\n";  //this always happens once
 cin >> response;                    //this always happens once
} while( !isvalid(response);     //and they will happen again if condition is not met.   

the do-while is messy to replace with other loop types because you have to 'seed' the 'happens one time no matter what' part.
the above as a for loop:
//do it one time out of the loop
cout << "enter something\n"; //this always happens once
cin >> response; //this always happens once
for(; !isvalid(response);) //if the response is no good, loop until they get it right
{
cout << "enter something\n"; //this always happens once
cin >> response; //this always happens once
}

if you find yourself doing it once outside the loop and again inside, then you should have used the do-while.

the ranged based for loop is used with containers, to touch every item in them. You can ignore this type for now, and an example would take more explaining than I care to do right now assuming you have not even seen a vector yet...