如何确定一个数字是否为二进制数并且只有一个正则表达式且有偶数个零？

Question

I want a regex to determine if a number is binary and if it has an even amount of zeros in it.

For example, if we consider these 3 numbers:

• 10001010
• 00010010
• 45671892

I want the regex to match the following:

• 10001010 //Does NOT match because it has an uneven amount of zeros
• 00010010 //Does match because it has an even amount of zeros
• 45671892 //Does not match because it is not a binary number

The current solution is the following:

[1]*(0[1]*0[1]*)*

I tested it with https://regex101.com/ and it works for me. The question is still online just to see if anyone can come up with a more efficient solution

I am thankful for every help.

Thank you in advance!

Answer 1

^[1]*(0[1]*0[1]*)*$

which can be interpreted in the following way:

find any number of 1 followed by pairs of 00 with optional one or more 1 s in between.

Answer 2

You can use Long#parseLong to check if the given number string represents a binary number or not. If yes, you can get a stream out of the number string, filter for 0 , count the number of 0 s and check if the count is divisible by 2 or not to determine if it has odd or even number of 0 s.

public class Main {
    public static void main(String[] args) {
        String[] arr = { "10001010", "00010010", "45671892" };

        for (String s : arr) {
            // Check if the number string is binary
            try {
                // Can validate up to 64 bits
                Long.parseLong(s, 2);
                if (s.chars().filter(c -> c == '0').count() % 2 == 0) {
                    System.out.println(s + " represents a binary number and has an even number of 0s.");
                } else {
                    System.out.println(s + " represents a binary number and has an odd number of 0s.");
                }
            } catch (Exception e) {
                System.out.println(s + " does not represent a binary number.");
            }
        }
    }
}

Output:

10001010 represents a binary number and has an odd number of 0s.
00010010 represents a binary number and has an even number of 0s.
45671892 does not represent a binary number.