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Quark 13Dec2010 12:37

Sum numbers recursively
 
I have been brushing up on recursion. I have a typical problem here. I want to sum up all the numbers between two bounds.The end bounds are included in the sum. I have here a small program to the do the above. Except it goes into infiinite loop. Here is the listing:

Code:

#include <stdio.h>

int sum(int a,int b)
{
        if(a>=b)
                return 0;
        result= a+sum(++a,b);
        return result;
}

int main()
{
        int i,j,r=0;
        printf("Enter the range: ");
        scanf("%d %d",&i,&j);
        printf("The result is :",sum(i,j));
        getch();
        return 0;
}


k1e1g1 13Dec2010 13:14

Re: Sum numbers recursively
 
I'm new to this, but I believe it's because you did not define 'result'. If you were to define it as an int, that may solve your problem.
Alternately, you could leave result out all together and just
return a+sum(++a,b);

Quark 13Dec2010 13:20

Re: Sum numbers recursively
 
Actually I removed the result altogether ......... still the same result.

Quark 13Dec2010 13:33

Re: Sum numbers recursively
 
#include <stdio.h>
#include <conio.h>

int sum(int a,int b)
{
if(a>=b)
return 0;
return a+sum(++a,b);
}

int main()
{
int i,j,r=0;
printf("Enter the range: ");
scanf("%d %d",&i,&j);
printf("The result is :",sum(i,j));
getch();
return 0;
}

##########Still loops infinitely##############

jimblumberg 13Dec2010 23:15

Re: Sum numbers recursively
 
The following code:
Code:

return a+sum(++a,b);
Is your problem. The ++a in this position is undefined.

Code:

int temp = sum(++a,b)
return a+temp;

See this link: Sequence points

Jim

Quark 15Dec2010 19:31

Re: Sum numbers recursively
 
I solved this problem this way.

int inc(int a)
{
return ++a;
}


#include <stdio.h>

int sum(int a,int b)
{
if(a>=b)
return 0;
result= a+sum(inc(a),b);
return result;
}

int main()
{
int i,j,r=0;
printf("Enter the range: ");
scanf("%d %d",&i,&j);
printf("The result is :%d",sum(i,j));
getch();
return 0;
}


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