Split a phone number into three groups

Question

I have a problem with a program that should split a phone number(ex. 1231231234) that user enters into three groups and display them like this (123)-123-1234. I'm not sure how to split this number and what to use in order to complete it. I didn't completed the code party but here's what i got.

#define SIZE 3
int main(void){
        int option, j;
        int phList = 0;
        int phoneNum[SIZE];
        printf("---=== Phone Numbers ===---\n");
        while(1){
                printf("\n");
                printf("1. Display Phone List\n");
                printf("2. Add a Number\n");
                printf("0. Exit\n");
                printf("\n");
                printf("Please select from the above options: ");
                scanf("%d", &option);
                if(option == 0){
                        printf("Exiting Phone Number App. Good Bye!!!\n");
                        return 0;
                }
                if(option == 1){
                        printf("\n");
                        printf("Phone Numbers\n");
                        printf("==============\n");
                        for(j = 0; j < phList; j++){
                                printf("\n", phoneNum[j]);
                        }
                }
                if(option == 2){
                        if(phList < SIZE){
                                printf("\n");
                                printf("Add a Number\n");
                                printf("============\n");
                                scanf("%d", &phoneNum[phList]);
                                phList++;
                                } else {
                                        printf("Add a Number\n");
                                        printf("============\n");
                                        printf("ERROR!!! Phone Number List is F$
                                        }
                }
        }
return 0;
}

Answer 1

I would consider using fgets() to get the phone number as a string, rather than getting it as an integer. Then you can filter the input so that only the digits are kept, allowing users to enter parenthesis, spaces, or dashes as desired. Finally, sscanf() can be used to scan the filtered string into three strings for the area code, exchange number, and subscriber number. If you like, these strings can be converted to numbers by atoi() or strtol().

The OP seems to be assuming that the phone number follows the format of the North American Numbering Plan, but phone number formats may differ. The string representation is more flexible than an integer representation, making future modifications to the code easier.

Here is an example of how this might be done:

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

void filter_num(char *str);

int main(void)
{
    char buffer[1000];
    char area_code[4];
    char xch_num[4];
    char sub_num[5];

    printf("Enter phone number: ");
    if (fgets(buffer, sizeof buffer, stdin) == NULL) {
        fprintf(stderr, "Error in fgets\n");
        exit(EXIT_FAILURE);
    }

    filter_num(buffer);
    if (sscanf(buffer, "%3s%3s%4s", area_code, xch_num, sub_num) != 3) {
            fprintf(stderr, "Phone number format error\n");
            exit(EXIT_FAILURE);
        }

    printf("Phone number is: (%s) %s-%s\n",
           area_code, xch_num, sub_num);

    return 0;
}

void filter_num(char *str)
{
    char *p = str;
    while (*p != '\0') {
        if (isdigit(*p)) {
            *str++ = *p;
        }
        ++p;
    }
    *str = '\0';
}

Answer 2

I will suggest defining a function to split the number and display that, Please have a look on this one, I have written it for you just now and works fine:

 void DisplayNum(long long int PhNum)
 {

   printf("\n ");

   for(int i=1; i<=10; ++i)   // Since Phone Number Contains 10 digits
  {
    int digit= PhNum/(pow(10,10-i));     // Spliting digits
    digit= digit%10;

    if(i==1)
     {
        printf(" (");
     }

     if(i==4)
     {
        printf(")-");
     }

     if(i==7)
    {
        printf("-");
    }

    printf("%d",digit);             // Displaying Digits
  }

 }

But make sure to use #include<math.h> at the beginning because i am using pow() function here. Then you can just pass each Phone Number in array to display to this function. The for-loop to display each Phone Number in array will be like :

 for(j = 0; j < phList; j++){
                                DisplayNum(phoneNum[j]);
                              }