# Sum numbers recursively

Discussion in 'C' started by Quark, Dec 13, 2010.

1. ### QuarkNew Member

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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;
}```

Last edited by a moderator: Dec 13, 2010
2. ### k1e1g1New Member

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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);

3. ### QuarkNew Member

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Actually I removed the result altogether ......... still the same result.

4. ### QuarkNew Member

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#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##############

5. ### jimblumbergNew Member

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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;```

Jim

6. ### QuarkNew Member

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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;
}