Question

In C program. Read and convert a sequence of digits to its equivalent integer. Any leading white space should be skipped. The conversion should include digit characters until a non-digit character is encountered. Modify the program so it can read and convert a sequence of digit characters preceded by a sign, + or -.

Answer 1

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

int main ()
{
   char string1[100], string2[100];
   printf("Enter the string of digits with numbers :: ");
   scanf("%s", string1);
   int i, stringLen, num = 0, j;
   stringLen = strlen(string1);
   for(i = 0, j = 0; i < stringLen; i++) {
        if (isspace(string1[i])) { }
        else if (isdigit(string1[i])) {
              string2[j] = string1[i];
              j++;
        }
       else
           break;
   }
    num = atoi (string2);
    printf ("The string value in digit is = %d", num);
}

/******************** OUTPUT OF PROGRAM ***********************
Enter the string of digits with numbers ::    502414
The string value in digit is = 502414
**************************************************************/

// Modified for + or - sign

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

int main ()
{
   char string1[100], string2[100];
   printf("Enter the string of digits with numbers :: ");
   scanf("%s", string1);
   int i, stringLen, num = 0, posflag = 0, j;
   stringLen = strlen(string1);
   for(i = 0, j = 0; i < stringLen; i++) {
        if (isspace(string1[i])) { }
        else if (string1[i] == '-') {
           posflag++;
       }
        else if (isdigit(string1[i])) {
              string2[j] = string1[i];
              j++;
        }
   }
    num = atoi (string2);
    num = posflag ? (num * (-1)) : num;
    printf ("The string value in digit is = %d", num);
}

/******************* OUTPUT OF PROGRAM *************************
Enter the string of digits with numbers ::      +102654
The string value in digit is = 102654

Enter the string of digits with numbers ::     -512415
The string value in digit is = -512415

***************************************************************/