非法文件：无法打开（/ dev / tty）USACO错误

Question

I'm working on a USACO online training problem and the grader gives me the following error:

Run 2: Execution error: Your program had this runtime error: Illegal file open (/dev/tty). The program ran for 0.000 CPU seconds before the error. It used 2160 KB of memory.

The program works on my computer (Windows 8: Codeblocks, mingw) but not on the grader machine (Linux). Even weirder is that test 1 worked fine but the error appears on run 2. Based on the related USACO help page, the error is most likely due to some out-of-bound array indexing, but I'm unable to find the error. My input file is just two integers separated by a space, followed by a newline (in this case the input is 9 10 ), and the output file looks like

15
16
17
18
20
21
24
26
27

Here's my code:

/*
TASK:dualpal
LANG:C
ID:tanishq1
*/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>

#include <string.h>

void strreverse(char * str)
{
  if (str)
  {
    char *end = str + strlen(str) - 1;

    // swap the values in the two given variables
    // XXX: fails when a and b refer to same memory location
#   define XOR_SWAP(a,b) do\
    {\
      a ^= b;\
      b ^= a;\
      a ^= b;\
    } while (0)

    // walk inwards from both ends of the string,
    // swapping until we get to the middle
    while (str < end)
    {
      XOR_SWAP(*str, *end);
      str++;
      end--;
    }
#   undef XOR_SWAP
  }
}

int palindromecheck(char *palstring) {
    char *reversepalstring;
    reversepalstring = (char *)malloc(sizeof(palstring) * sizeof(char));
    strcpy(reversepalstring,palstring);
    strreverse(reversepalstring);
    if (strcmp(reversepalstring,palstring) == 0) {
        return 1;
    }
    else {
        return 0;
    }
}

char returnstring[34];

char *baseconvert(int number,int base) {
    if(number == 0 || base == 10) {
        sprintf(returnstring,"%d",number);
        return returnstring;
    }
    int returnint = (number % base) + (10 * atoi(baseconvert(number / base, base)));
    sprintf(returnstring,"%d",returnint);
    return returnstring;
}

int main() {
    FILE *inputfile = fopen("dualpal.in","r");
    FILE *outputfile = fopen("dualpal.out","w");

    int n;
    int s;
    fscanf(inputfile,"%d %d\n",&n,&s);
    int i = 1, ncounter = 0, scounter = 1;
    for (i; ncounter < n; i++) {
        int j = 2;
        int palindromesuccesscounter = 0;
        for (j; j <= 10; j++) {
            int palindrome = palindromecheck(baseconvert(s + scounter, j));
            if (palindrome == 1) {
                palindromesuccesscounter++;
            }
        }
        if (palindromesuccesscounter > 1) {
            fprintf(outputfile,"%d\n",s + scounter);
            ncounter++;
        }
        scounter++;
    }

    fclose(inputfile);
    fclose(outputfile);
    return 0;
}

Answer 1

Based on the related USACO help page, the error is most likely due to some out-of-bound array indexing

In your palindromecheck function, you have:

int palindromecheck(char *palstring) {
    char *reversepalstring;
    reversepalstring = (char *)malloc(sizeof(palstring) * sizeof(char));
    ...
}

palstring is a pointer, not an array, and sizeof(palstring) will give you the size of a pointer (likely 4 or 8 bytes), not the length of the string.

You need to use strlen to determine the length of the string (and add 1 to allow for the terminating '\\0' null character).