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While trying to submit my 3n+1 code, I keep on getting a runtime error although it works perfectly with a huge number of sample input. I've spent lots of time trying to spot the error but I can't find it. Can anybody help?

#include <stdio.h>

#define SIZE 10000 


unsigned short countCycle(long num); /* prototype for a fn that gets int and returns the cyleLength */

unsigned short greatest,cyclyeLength; /* greatest for holding greatest cycyle */
unsigned short table[SIZE]; /* storing sequances with indecies up to 10,000 */
long temp;/* temp storage */
short flag;/* n>m or not */

int main (int argc,char* argv[])
{
    long n,m,i; 

    while(scanf("%lu %lu",&n,&m) != EOF)
    {
        greatest = 0;
        if(n>m)
        {
            temp = n; n=m; m=temp;
            flag = 1;
        }

        for (i=n;i<=m;i++)
        {
            temp = countCycle(i);
            greatest = (greatest>temp) ? greatest:temp;
        }
        if(flag == 1)
            printf("%lu %lu %d\n",m,n,greatest);
        else
            printf("%lu %lu %d\n",n,m,greatest);

        while(getchar() != '\n') /* clear the input stream */
            continue;

    }
    return(0);
}

unsigned short countCycle(long num)
{
    temp = num;
    cyclyeLength = 0;
    while(1)
    {

        if(num == 1)
        {
            cyclyeLength++;
            if(temp<SIZE)
                table[temp] = cyclyeLength;
            return cyclyeLength;
        }

        if((num<SIZE) && (table[num]>0)) 
        {
            table[temp] = (cyclyeLength + table[num]);
            return (cyclyeLength + table[num]);
        }

        if( num % 2 != 0 )
        {
            num = 3*num + 1;
            cyclyeLength++;
        }
        if( num % 2 == 0 )
        {
            num/=2;
            cyclyeLength++;
        }



    }

}
thmas
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user2534634
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  • And it doesn't work with a small number of inputs? How small a number? Does it work when you run it? Was there any warnings when you compiled the program (turning on many warnings can indicate undefined behaviors)? – Some programmer dude Jun 30 '13 at 13:32
  • 1
    Also note that your `while (scanf(...) != EOF)` loop may be misleading. What if there is *not* two items to be scanned? Then `scanf` will return 1. You should loop while the return value is equal to two. – Some programmer dude Jun 30 '13 at 13:35

0 Answers0