Recursive c++

[mickey4691]

Given an integer n>0, write a recursive C++ function that writes the integers 1,2,...,n.?

#include <iostream>
using namespace std;
int d(int);
int main()
{
	int n;
	cout<<"Enter a whole number: ";
	cin>>n;
	for (int i=1;i<=n;i++)
	{ cout<<"The preceeding numbers are: "<<d(i); }
	cout<<endl;
	return 0; 
}
int d(int n)
{
	if (n<=0)
	return 0;
	else 
	 return d(n);
}

[zsteve]

This is fairly simple :

This example uses "tail recursion", that is, the recursive step occurring before the processing (except for the exiting condition). Tail recursion is useful for doing things "backwards", i.e. this example, when you have 'n' and you want to go from 1 to n.
("forwards" here would be going from n to 1).

Hope that helped :)

#include <iostream>

using namespace std;

int rec_print(int n){
	if(n==1) return 0;
	rec_print(n-1);
	cout << n << endl;
	return 0;
}

int main(){
	int n;
	cout << "n?" << endl << '>' ;
	cin >> n;
	rec_print(n);
}

[eyenrique]

Hi @mickey4691,
i do not know if
this is the best
solution but it works;

Pseudo code

number entered: 3

function(3) //step 1
    if 3 > 1 
        call:  function(3-1)  //step 2
        print<<3<<space;  //this is waiting until step 2 finish
   else  //never happens 
           print<<number<<space;

//step2
function(2)
   if 2>1
     call:  function(2-1) //step 3
     print<<2<<space;  //this is waiting until step 3 finish
  else //never happens
     print<<number<<space;

//step 3
function(1)
  if 1>1  //1 is NOT greater than 1 so..
    call: function(1-1) //there are not step 4
    print<<number<<space; //never happens
else //print number 1 
    print<<1<<space; //this is the first output
                                //followed by the rest that are waiting: 2,3

Console

Eyenrique-MacBook-Pro:Desktop Eyenrique$ ./RecNum 
Enter a number (greater than zero): 3
1 2 3 

Code

//RecNum.cpp
//##

#include <iostream>
using std::cout;
using std::cin;
using std::endl;


bool numberIsGreaterThanZero(int number);

void RecursiveSequence(int number);

int main(){

int number;

        cout<<"Enter a number (greater than zero): ";
        cin>>number;

        if(numberIsGreaterThanZero(number)){
                RecursiveSequence(number);    
        }else{
                cout<<"Is not greater than zero!"<<endl;
        }//end if-else

        cout<<endl;


return 0; //indicates success
}//end main


bool numberIsGreaterThanZero(int number){
        if(number>0)return true;

return false;
}//end function numberIsGreaterThanZero

void RecursiveSequence(int number){
        if(number>1){ //Recursive statement
                RecursiveSequence(number-1);
                cout<<number<<' ';
        }else{ //Base case [number equal to one]

                cout<<number<<' ';
            
        }//end if-else

}//end function RecursiveSequence 

[JLBorges]

#include <iostream>

void print_all_numbers_from_1_up_to( int n )
{
    if( n > 0 ) // if n is less than one, there is nothing to be printed
    {
        // we need to: print all numbers starting from from 1 up to n
        // how do we do that?

        // simple: first print all numbers starting from from 1 up to (n-1)
        print_all_numbers_from_1_up_to( n-1 ) ;

        // and finally, print the number n
        std::cout << n << '\n' ;
    }
}

int main()
{
    int n ;
    std::cout << "number? " ;
    std::cin >> n ;

    print_all_numbers_from_1_up_to(n) ;
}

[Manga]

I am not at my computer with my compilier so I can't test this...

However I might try something like this...

#include <iostream>
using namespace std;

void print_numbers_to_n(int n, int i) {
  if(i<n) {
    cout < i < endl;
    i++;
    print_numbers_to_n(n, i);
  }
  else {
    cout < n;
  }
}

int main() {
  int n;
  int i=1;

cout < "number? ";
cin > n;
print_numbers_to_n(n, i);
return 0;
}

[mickey4691]

Thank you all, especially @zsteve.
I figured it out though.