Re: Suggested method for returning a string from a C program?

I'm doing these algorithm problems at
https://cses.fi/problemset/list/
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For instance:  Weird Algorithm
https://cses.fi/problemset/task/1068
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My code works fine locally (prints the correct solution to the
console), but when I submit the .c file the auto-tester flags it with
runtime error' and says the output is empty.
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// If n is even, divide it by two.
// If n is odd, multiply it by three and add one.
// Repeat until n is one.
// n = 3: output is 3 10 5 16 8 4 2 1
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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
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int main(int argc, char *argv[])
{
int n = atoi(argv[1]);
int len = 0;
char result[10000] = "";
sprintf(result, "%d ", n);
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while(1) {
        if((n % 2) == 0)
            {n /= 2;}
        else
            {n = (n * 3) + 1;}
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        if(n != 1)
            {
                len = strlen(result);
                sprintf(result + len, "%d ", n);
            }
        else
            break;
}
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len = strlen(result);
sprintf(result + len, "1 ");
printf("%s\n",result);
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return 0;
}
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Any ideas?