How to Determine if a C String or char* Contains Only Digits?

How to Verify if a C String or char* Consists Exclusively of Digits

Question:

In C , is it possible to determine whether a given string or char* contains only numeric characters? If so, how do we find the first non-digit character, and do similar methods apply to both types?

Answer:

Yes, there are multiple techniques to assess if a string or char* consists solely of digits. Here are two potential approaches:

1. find_first_not_of() Method:

This method checks for the first occurrence of a non-digit character in the input. If the result is std::string::npos, it implies that all characters are digits.

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

2. std::all_of() Method (C 11 and above):

This method uses the std::all_of algorithm to test if each character in the input meets a particular condition, in this case, whether it's a digit.

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

Application to Both Types:

The methods discussed above can be utilized with both std::string and char types. However, it's crucial to ensure proper conversion or initialization when working with char to maintain consistency in data representation and prevent unintended behavior.

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