Trying to figure out how to output a phone number in c? - c

Question

I am trying to input a phone number and print it out in this format [phone] format but when i am trying to print it out i get some weird output that is not what i am expecting to get back out. I am printing out the values of phone both in the input and in the print function bt they are different. The one in the input function is correct but it isnt correct in the print function. Thanks in advance for the help.
int phoneInput(void)
{
long int phone = 0;
printf("Input the politicians phone number with no speaces: ");
scanf("%ld", &phone);
printf("test : %ld", phone);
return phone;
}
int printPhone(long int phone)
{
int i = 10; //the number of digits in the phone
char output[11];
printf("Test: %ld", phone);
for (i = 0; i < 10; i ++)
{
while (phone > 0)
{
output[i] = phone % 10;
phone /= 10;
}
}
printf("- Phone number: (");
i = 0;
for (i = 0; i < 3; i++)
{
printf("%d", output[i]);
}
printf(")");
i = 3;
for(i = 3; i < 6; i++)
{
printf("%d", output[i]);
}
i = 6;
printf("-");
for(i = 6; i < 10; i++)
{
printf("%d", output[i]);
}
return 0;
}

Answer 1

The only reason you'd need to store a value as an int, a long int, or another numeric type is if you had to do arithmetic on it (unless it's required by a homework assignment specification). Don't be fooled by the fact that a phone number is composed of numbers - it makes most sense to be stored as a string!
If you can store the phone number as a string, you should:
char *phoneInput(void)
{
static char phone[100];
printf("Input the politicians phone number with no spaces: ");
fgets(phone, 100, stdin);
return phone;
}
Once you have that, it's easier to control how it is printed:
printf("(%.3s) %.3s-%.4s\n", phone, phone + 3, phone + 6);

Answer 2

A phone number should be stored as country, area, subscriber.
The example you gave would be 1 888 9991111
And note that any leading 00 for a country number is actually the local method of instructing the switch to dial an international number. In Spain it used to be 9 for a long time. The generic identification for international number dialing is now +.
See also https://www.internationalcitizens.com/international-calling-codes/

Answer 3

Sarah, first of all I would scan phone number as string, it is easier to do it that way. Another reason to scan it as string long int might not be sufficient enough, on some platforms long is 32 bits. But if you require 'long int` the best way would be:
printf ("(%ld)", number / 10000000); // prints area code (xxx)
printf (" %ld-", (number / 1000) % 1000); // prints xxx-
printf ("%ld\n", number % 10000); // prints xxxx\n
another way would be:
fscanf( stdin, " %3s%3s%4s", areacode, zone, number);
printf("(%s) %s-%s\n", areacode, zone, number);

Answer 4

In your existing code, the problem lies in the loops:
for (i = 0; i < 10; i ++)
{
while (phone > 0)
{
output[i] = phone % 10;
phone /= 10;
}
}
Your inner loop will keep executing without incrementing i causing the same position in the array to be written again and again.
i = 9;
do
{
output[i] = (phone % 10) + '0';
phone /= 10;
i--;
}while((phone > 0) && (i >= 0));
Please use "%c" in the printf while printing output.
List of issues in the code posted by OP. These are just issues in the
code posted by OP. The logic can be done in many other ways, but, this
answer purely focuses on issues in OP's code as-is:
phoneInput function should return long int instead of int
for and while loop - Two loops are not needed. This is the main error. This causes same position in array to be overwritten each time.
Loop counter for array position starts from 0, causing digits to be written in reverse order in the array
Since, you are using a char array, store and print char instead of int.
Complete code with issues fixed (as per OP's original code):
#include <stdio.h>
#include <string.h>
long int phoneInput(void)
{
long int phone = 0;
printf("Input the politicians phone number with no spaces: ");
scanf("%ld", &phone);
printf("test : %ld\n", phone);
return phone;
}
int printPhone(long int phone)
{
int i = 10; //the number of digits in the phone
char output[11];
memset(output, '0', sizeof(output));
printf("Test: %ld\n", phone);
i = 9;
do
{
output[i] = (phone % 10) + '0';
phone /= 10;
i--;
}while( (phone > 0) && (i >= 0));
printf("- Phone number: (");
i = 0;
for (i = 0; i < 3; i++)
{
printf("%c", output[i]);
}
printf(")");
i = 3;
for(i = 3; i < 6; i++)
{
printf("%c", output[i]);
}
i = 6;
printf("-");
for(i = 6; i < 10; i++)
{
printf("%c", output[i]);
}
return 0;
}
void main()
{
long int phone;
phone = phoneInput();
printPhone(phone);
}
Output:
Input the politicians phone number with no spaces: 8889991111
test : 8889991111
Test: 8889991111
- Phone number: [phone]

Answer 5

I've made a few changes to your code. Please take a look.
long long int phoneInput(void)
{
long long int phone = 0;
printf("Input the politicians phone number with no speaces: ");
scanf("%lld", &phone);
printf("test : %lld", phone);
return phone;
}
int printPhone(long long int phone)
{
int i = 10; //the number of digits in the phone
char output[11];
printf("Test: %lld", phone);
i = 9; // removed for loop that was unnecessary.
while (phone > 0)
{
output[i] = phone % 10;
phone /= 10;
i--;
}
printf("- Phone number: (");
i = 0;
for (i = 0; i < 3; i++)
{
printf("%d", output[i]);
}
printf(")");
i = 3;
for(i = 3; i < 6; i++)
{
printf("%d", output[i]);
}
i = 6;
printf("-");
for(i = 6; i < 10; i++)
{
printf("%d", output[i]);
}
return 0;
}
int main(int argc, char const *argv[])
{
long long int n = phoneInput();
printPhone(n);
return 0;
}

Answer 6

void printTelephoneNumber(vector phoneNum) {
string phonePad[10] {
"000", "111", "ABC", "DEF", "GHI", "JKL", "MNO", "PRS", "TUV", "WXY"
};
size_t PHONE_NUMBER_LENGTH = phoneNum.size();
size_t LETTERS_PER_KEY = 3;
size_t maxcount = (size_t )pow(LETTERS_PER_KEY, PHONE_NUMBER_LENGTH);
// Could have used: colIndex[PHONE_NUMBER_LENGTH] = {0};
vector<int> letterIndex(PHONE_NUMBER_LENGTH, 0); // Use either name: colIndex or charIndex
for(int count=0; count<maxcount; count++) {
// print string
string str = "";
for(int i=0; i<PHONE_NUMBER_LENGTH; i++) {
str += phonePad[phoneNum[i]][letterIndex[i]];
}
cout << str << endl;
// Update next letter (column) indicies
int nextCount = count + 1; // next count
size_t i = PHONE_NUMBER_LENGTH - 1;
do {
letterIndex[i] = nextCount % LETTERS_PER_KEY;
nextCount = nextCount / LETTERS_PER_KEY;
i--;
} while(nextCount > 0);
}
}
Algorithm: There are 3^n combinations for n digits phone number. examples: phoneNum[n] = {2,3,4} => 3^3 = 27. Use extra space for tracking letters in a digit => letterIndex[PHONE_NUMBER_LENGTH]

Answer 7

while (phone > 0)
{
output[i++] = (phone % 10) + '0';
phone /= 10;
}
and
printf("%c", output[i]);
are the changes that need to be made in your code to make it work.
The first change (+ '0') is to convert from int to char.
The second one is because you want to print a char and not an int.
I advise you to check the manual of printf and the ascii table to understand better.