Programming Forums > Application Development > C++

cairo · Apr 13th, 2006, 1:26 PM

void printStar(int input)
{
    if (input >=0 )
    {
        printStar(input-1);      
       for(int i=1; i<=input; i++)
       {
               cout <<"*";
               }
       cout<<endl;
        
       }  
         
   }

i try to print the stars below with recursion, but i failed

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

i would appreciate, if i got hint from u all

a3orange · Apr 13th, 2006, 4:15 PM

Do you see this line:

(Toggle Plain Text)

void printStar(int input)
{
    if (input >=0 )
    {
        printStar(input-1);       
       for(int i=1; i<=input; i++)
       {
               cout <<"*";
               }
       cout<<endl;
        
       }  
         
   }

You keep recalling the function which makes it impossible to begin the for loop. You would probably want to do something like this..

(Toggle Plain Text)

void printStar(int input)
{
    if (input >=0 )
    {
           
       for(int i=1; i<=input; i++)
       {
               cout <<"*";
               }
       printStar(input-1);   
       cout<<endl;
        
       }  
         
   }

Edit: Wait, did you want to print this:

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

If so, you're going to have to do some more stuff.

hbe02 · Apr 13th, 2006, 6:01 PM

must disagree with you there, the code correction you posted is incorrect, this is not how recursion is done. in regards to the problem, the approach is correct, you have called the function recursively till you reach 0 then print line by line form 1 start up to 'input' stars .. this only gives half the figure unfortunately, i cant think of a a way to do it recursively. but if you want the end product to be
*
**
***
***
**
*
then just do a for-loop for the bottom part in main

(Toggle Plain Text)

for (int i = input ; i >=1 ; i--)

DaWei · Apr 13th, 2006, 6:59 PM

(Toggle Plain Text)

void printStar(int count, int limit)
{
    for (int i = 0; i < limit-count; i++) cout << '*';
    cout << endl;
    if (count ) printStar (count-1, limit);
    for (int i = 0; i < limit-count; i++) cout << '*';
    cout << endl;
}
int main (int argc, char *argv [])
{
    printStar (5, 5);
    puts ("Press ENTER to terminate\n");
    getchar ();
    return 0;
}

Quote:

Originally Posted by output

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

Press ENTER to terminate

cairo · Apr 14th, 2006, 10:39 AM

thanks u all guys, i got a clue from dawei
thanks a lot ^^

Apr 13th, 2006, 1:26 PM	#1
cairo Newbie Join Date: Dec 2005 Posts: 18 Rep Power: 0	problem with printstar (Toggle Plain Text) void printStar(int input) { if (input >=0 ) { printStar(input-1); for(int i=1; i<=input; i++) { cout <<""; } cout<<endl; } } void printStar(int input) { if (input >=0 ) { printStar(input-1); for(int i=1; i<=input; i++) { cout <<""; } cout<<endl; } } i try to print the stars below with recursion, but i failed * * * * i would appreciate, if i got hint from u all

Apr 13th, 2006, 4:15 PM	#2
a3orange Newbie Join Date: Apr 2006 Posts: 14 Rep Power: 0	Do you see this line: (Toggle Plain Text) void printStar(int input) { if (input >=0 ) { printStar(input-1); for(int i=1; i<=input; i++) { cout <<""; } cout<<endl; } } void printStar(int input) { if (input >=0 ) { printStar(input-1); for(int i=1; i<=input; i++) { cout <<""; } cout<<endl; } } You keep recalling the function which makes it impossible to begin the for loop. You would probably want to do something like this.. (Toggle Plain Text) void printStar(int input) { if (input >=0 ) { for(int i=1; i<=input; i++) { cout <<""; } printStar(input-1); cout<<endl; } } void printStar(int input) { if (input >=0 ) { for(int i=1; i<=input; i++) { cout <<""; } printStar(input-1); cout<<endl; } } Edit: Wait, did you want to print this: * * * * If so, you're going to have to do some more stuff.

Apr 13th, 2006, 6:01 PM	#3
hbe02 Hobbyist Programmer Join Date: Mar 2006 Location: Lebanon Posts: 148 Rep Power: 3	must disagree with you there, the code correction you posted is incorrect, this is not how recursion is done. in regards to the problem, the approach is correct, you have called the function recursively till you reach 0 then print line by line form 1 start up to 'input' stars .. this only gives half the figure unfortunately, i cant think of a a way to do it recursively. but if you want the end product to be * * * * then just do a for-loop for the bottom part in main (Toggle Plain Text) for (int i = input ; i >=1 ; i--) for (int i = input ; i >=1 ; i--)

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Apr 14th, 2006, 10:39 AM	#5
cairo Newbie Join Date: Dec 2005 Posts: 18 Rep Power: 0	thanks u all guys, i got a clue from dawei thanks a lot ^^

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Programming Forums > Application Development > C++

problem with printstar