Question

I am writing a program to validate a CSV file. The limitations on the format are:

• A line cannot end with a comma, it must end with a digit;
• A line cannot start with a comma, it must be a digit;
• A line can be blank;
• Only single digits are allowed as numbers (i.e. no numbers below 0 or greater than 9);
• Two commas cannot be next to each other, they must be separated by a digit.

EDIT:

I have made some changes to the code based on the feedback. Can someone please explain what the while loop is actually doing? And why isn’t the switch working? I am now getting 1’s for all input. Can I use isdigit in the switch?

#include <ctype.h>
#include <stdio.h> 

int main()
{

int c;

    while ((c = getchar()) != EOF )
    {      
        switch(c)
    {
        case'0':
            printf("1");
            break;
        case'1':
            printf("1");
            break;
        case'2':
            printf("1");
            break;
        case'3':
            printf("1");
            break;
        case'4':
            printf("1");
            break;
        case'5':
            printf("1");
            break;
        case'6':
            printf("1");
            break;
        case'7':
            printf("1");
            break;
        case'8':
            printf("1");
            break;
        case'9':
            printf("1");
            break;
        case',' :
            printf("1");
            break;
        case'\n' :
            printf("1");
            break;
        default :
            printf("0");
            break;
    }
}
}

Answer 1

#include <stdio.h>
#include <string.h>
#include <ctype.h>

#define bool int
#define false 0
#define true !false

// Rule:(SPACE* | [0-9](,[0-9])*)CR
bool isValid(char *str){
    if(*str == '\n')
        return true;
    if(*str == ' '){
        while(*++str == ' ');
        if(*str == '\n')
            return true;
        else
            return false;
    }
    if(isdigit(*str++)){
        do{
            if(*str == '\n')
                return true;
        }while(*str++ == ',' && isdigit(*str++));
        return false;
    }
    return false;
}

#define BUFF_SIZE 128

int main(void){
#ifdef DEBUG
    printf("\nEnd with comma:\n");
    printf(isValid("1,2,3,\n") ? "OK" : "NG");
    printf("\nStart with comma:\n");
    printf(isValid(",1,2,3\n") ? "OK" : "NG");
    printf("\nCR only:\n");
    printf(isValid("\n") ? "OK" : "NG");
    printf("\nSPACE and CR only:\n");
    printf(isValid("     \n") ? "OK" : "NG");
    printf("\nBelow zero:\n");
    printf(isValid("-1\n") ? "OK" : "NG");
    printf("\nGreater than nine:\n");
    printf(isValid("10\n") ? "OK" : "NG");
    printf("\nInclude two comma:\n");
    printf(isValid("3,4,,5\n") ? "OK" : "NG");
    printf("\nNormal pattern I:\n");
    printf(isValid("9\n") ? "OK" : "NG");
    printf("\nNormal pattern II:\n");
    printf(isValid("3,4,5\n") ? "OK" : "NG");
#else
    char line[BUFF_SIZE];
redo:
    fgets(line, BUFF_SIZE, stdin);
    if(NULL==strchr(line, '\n')){
        fprintf(stderr,"You have exceeded the number of characters that can be entered.\n");
        fflush(stdin);
        goto redo;
    }
    if(isValid(line))
        printf("OK\n");
    else
        printf("NG\n");
#endif
    return 0;
}