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[rahul820]

Why My Sum Value Didnt Update???
its still show me the first one....!!!!!!!!

#include<iostream>>

using namespace std;

class test{
    public:
        int series(int n){
            int sum=0;
            if(n==0) return 0;

            else{
                sum=sum+n;
                series(n-1);
                cout<<n<<" + ";
            }
            return sum;

        }
};

int main(){
    test p;
    int n;
    cout<<"Enter N ";
    cin>>n;
    cout<<endl<<"Sum Is "<<p.series(n);

}

[AbstractionAnon]

Line 13: You make a recursive call to series(), but you're ignoring the return result.

How are you going to get the result of the recursive call if you ignore the result?

[DyslexicChciken]

You probably meant it to be tail recursive. If so you need to pass sum as an accumulating parameter:

#include<iostream>

using namespace std;

class test
{

    public:

    //sum accumulates the previous sums and is passed to the next recursive level
    int series(int n, int sum) 
    {
        //the cout statements show you that upward propagation does not happen.
        cout << "n: " << n << ' '
             << "sum: " << sum << endl;

        //the function is returned at the last recursive level,
        //so you don't propagate upward. Hence it is called tail recursive.
	if(n==0) return sum; 

	else
	{
	    sum = sum + n;
	    series(n-1, sum);

  	}

  }
};

int main()
{
	test p;
	int n;
	int sum = 0;

	cout << "Enter n: ";
	cin >> n;
	cout << endl << "Sum is " << p.series(n, sum);

}