C++ code for right triangle using WHILE loop

Question

I need to print this triangle:

*
**
***
****
*****
******
*******
********

using a FOR and WHILE loop. I need help, I have already figured out the for loop version I just have to convert it to while loop but everything I try is not giving me the correct output! Any help is appreciated!

My code so far:

#include <iostream>
using namespace std;
int main(int argc, char**argv) {

    int i = 1;
    int j = 1;
    int N = 8;

    while (i <= N)
    {
        i = i++;
        while(j <= i)
        {
            cout<<"*";
            j = j++;
        }
        cout<<endl;
    }
}

this is the triangle, i don't know if it showed up (right triangle) * ** *** — future, Aug 26 '11 at 20:13
you don't need `i = i++` and `j = j++`. just `i++` and `j++` will do the trick. — K Mehta, Aug 26 '11 at 20:17
`j = j++` says "increment `j`, then assign `j` the value it had before incrementing it." Probably not what you want. — Max Lybbert, Aug 26 '11 at 20:20

score 3 · Answer 1 · edited May 23 '17 at 12:28

I'll give you a hint (in the interest of making you do some figuring out yourself): You're forgetting to set j back to 1 after the inner loop.

As it is now, when j gets to be <= i once, it stays that way and the inner loop is never entered again.

Also, while it's not directly related to your question, make sure never to do j = j++ or i = i++; just do j++ and i++ (as Kshitij Mehta said in the comments). If you're interested in why, you can read this question and its answers.

score 1 · Answer 2 · answered Aug 26 '11 at 20:19

1

I'll give you a hint as well: i = i++; doesn't do what you think it does.

answered Aug 26 '11 at 20:19

Jon

3,065
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Bo Persson · Accepted Answer · 2011-08-26T20:43:22.057

1

What are the rules?

while (1)
{
    cout << "*" << '\n';
    cout << "**" << '\n';
    cout << "***" << '\n';
    cout << "****" << '\n';
    cout << "*****" << '\n';
    cout << "******" << '\n';
    cout << "*******" << '\n';
    cout << "********" << '\n';

    break;
}

edited Aug 26 '11 at 20:43

answered Aug 26 '11 at 20:34

Bo Persson

90,663
31
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203

score 0 · Answer 4 · edited Aug 26 '11 at 20:23

0

I can't see your triangle, but I think you need to set j to 1 before each loop on j:

while (i <= N)
{
    i++;
    j = 1;
    while(j <= i)
    {
        cout<<"*";
        j++;
    }
    cout<<endl;
}

edited Aug 26 '11 at 20:23

Seth Carnegie

73,875
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answered Aug 26 '11 at 20:18

Nicolas Grebille

1,332
8
15

3

When it's a homework question, try to encourage the OP to come up with the right answer by giving hints, and not the actual answer (like Seth did). – K Mehta Aug 26 '11 at 20:21
@kshitij OK, it make sense (the homework flag was added after but I could have guessed) – Nicolas Grebille Aug 26 '11 at 20:24
@teebee Glad it helped; don't forget to correct the `i=i++` statements like the others said (I copy/pasted your code without paying attention). – Nicolas Grebille Aug 26 '11 at 20:26

score 0 · Answer 5 · answered Aug 26 '11 at 20:20

0

I don't really know how to make it more succinct than this:

#include <iostream>
#include <sstream>

int main()
{
    std::stringstream ss;
    int i = 10;
    while (i--)
        std::cout << (ss<<'*', ss).str() << std::endl;
}

or as for loop, cutting down a line

for(int i=10; i--;)
        std::cout << (ss<<'*', ss).str() << std::endl;

If you don't mind some less efficient code:

#include <iostream>
int main() { for(int i=1; i<10; std::cout << std::string(i++, '*') << std::endl); }

answered Aug 26 '11 at 20:20

sehe

374,641
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1

While that's a very concise solution, it is not very legible _especially_ for someone who's just learning C++. – K Mehta Aug 26 '11 at 20:23
Uhoh, I knew that :) But hey, it's like homework, and if I'm going to spoil the fun, I better make it interesting along the way. It worked for me that way :) – sehe Aug 26 '11 at 20:24

score -1 · Answer 6 · edited Jan 08 '19 at 01:42

-1

#include <iostream>   

using namespace std;    

int main() 
{
    int i, j, N=7;  
    while(i <= N)
    {  
        i++;  
        j = 1;  
        while(j <= i)
        {
            cout << "*";  
            j++;
        }
        cout << endl;  
    }  
}

edited Jan 08 '19 at 01:42

סטנלי גרונן

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answered Jan 07 '19 at 18:20

user10880661

1

Variable "i" is not initialized. – סטנלי גרונן Jan 07 '19 at 18:45

C++ code for right triangle using WHILE loop

6 Answers6