Program to check if a number belongs to a particular base or not

Difficulty Level : Medium
Last Updated : 27 Sep, 2021

Given a number N and its radix base R, find whether its valid or not according to its radix base.
Find valid/invalid number for any base ranging from binary to base32.

Examples:

Input : 1000101010001
Output : Valid
1000101010001 is valid binary number.

Input : 0xFFFAG
Output : invalid
0xFFFAG is not a valid hexa-decimal number because of character 'G' .

Method used : strspn

strspn :

strspn(numStr, validNumber)
Strspan: 
returns number of matching digits from 
character-set provided, so here it will return 1 - N,
where N is length of validNumber String.
numStr[]  : 
And that number is provided to numStr[] array.

numStr :

numStr[strspn(numStr, validNumber)]
Using this number as index for numStr[] array,
we access the digit there and it will be NULL 
in case string is matched and it will be non-zero 
if string is not matched

!numStr : And Finally we invert the result using invert operator to match for true case !

!numStr[strspn(numStr, validNumber)]

C++

// Program to check if a number belongs
// to particular base or not#include
 
#include <cstdio>
#include <cstdlib>
#include <cstring>
 
#define BINARY_BASE 2 // Defining binary base
#define OCTAL_BASE 8 // Defining octal base
#define DECIMAL_BASE 10 // Defining decimal base
#define HEXA_BASE 16 // Defining hexa-decimal base
#define BASE32_BASE 32 // Defining base32 base
 
// Function prototypes
bool isValid(const char* numStr, int base);
const char* print(bool status);
 
// Main method for base check
int main(void)
{
    // Defining valid/invalid numbers in radix bases
    char* binaryStr = "1000101010001";
    char* decimalStr = "45221";
    char* base32Str = "AD22F";
 
    // invalid
    char* octalStr = "7778A";
    char* hexStr = "FAG463";
 
    // Printing status of radix bases
    printf("Binary string %s is %s\n", binaryStr,
           print(isValid(binaryStr, BINARY_BASE)));
    printf("Octal string %s is %s\n", octalStr,
           print(isValid(hexStr, OCTAL_BASE)));
    printf("Decimal string %s is %s\n", decimalStr,
           print(isValid(decimalStr, DECIMAL_BASE)));
    printf("Hex string %s is %s\n", hexStr,
           print(isValid(hexStr, HEXA_BASE)));
    printf("Base32 string %s is %s\n", base32Str,
           print(isValid(base32Str, BASE32_BASE)));
 
    return 0;
}
 
bool isValid(const char* numStr, int base)
{
    // Defining valid base strings
    const char* validBinary = "01";
    const char* validOctal = "01234567";
    const char* validDecimal = "0123456789";
    const char* validHex = "0123456789abcdefABCDEF";
    const char* validBase32 = "0123456789abcdefghijklmnopqrstuvABCDEFGHIJKLMNOPQRSTUV";
    const char* validNumber = NULL;
 
    // Checking for valid base
    validNumber = (base == BINARY_BASE)
                      ? validBinary
                      : ((base == OCTAL_BASE)
                             ? validOctal
                             : (base == DECIMAL_BASE)
                                   ? validDecimal
                                   : (base == HEXA_BASE)
                                         ? validHex
                                         : (base == BASE32_BASE)
                                               ? validBase32
                                               : NULL);
 
    // Error checking for invalid base
    if (validNumber == NULL) {
        fputs("Invalid base encountered", stderr);
        exit(EXIT_FAILURE);
    }
 
    // Check for valid base string using strspn
    return (!numStr[strspn(numStr, validNumber)]) ? true : false;
}
 
const char* print(bool status)
{
    return (status) ? "Valid" : "Invalid";
}

Output:

Binary string 1000101010001 is Valid
Octal string 7778A is Invalid
Decimal string 45221 is Valid
Hex string FAG463 is Invalid
Base32 string AD22F is Valid

We provide nothing but the best curated videos and practice problems for our students. Check out the C Foundation Course and master the C language from basic to advanced level. Wait no more, start learning today!

My Personal Notes

Related Articles

Program to check if a number belongs to a particular base or not

C++