How Can I Verify if a String or char* Contains Only Digits in C ?

Checking for Digit-Only Strings in C

Determining whether a string or char* contains only digits is a common task in programming. This article explores two efficient approaches:

1. Using find_first_not_of

This method iterates through the string, searching for the first non-digit character. If none is found (find_first_not_of("0123456789") returns std::string::npos), the string is considered digit-only:

<code class="cpp">bool is_digits(const std::string &amp;str)
{
    return str.find_first_not_of("0123456789") == std::string::npos;
}</code>

2. Using std::all_of (C 11 onwards)

This method utilizes a predicate to check each character of the string. In this case, the predicate is ::isdigit, which returns true for digit characters:

<code class="cpp">bool is_digits(const std::string &amp;str)
{
    return std::all_of(str.begin(), str.end(), ::isdigit); // C++11
}</code>

Do the Functions Apply to Both Strings and char*?

Yes, these functions can be used for both std::string and char* with minor modifications. For char*, the std::string constructor can be used to convert the char* to a std::string:

<code class="cpp">bool is_digits(const char *str)
{
    std::string str_copy(str);
    return is_digits(str_copy);
}</code>

The above is the detailed content of How Can I Verify if a String or char* Contains Only Digits in C ?. For more information, please follow other related articles on the PHP Chinese website!