Given a string of 0 and 1, we need to check that the given string is valid or not. The given string is valid when there is no zero is present in between 1’s. For example, 1111, 0000111110, 1111000 are valid strings but 01010011, 01010, 101 are not.
Examples:
Input : 100 Output : VALID Input : 1110001 Output : NOT VALID There is 0 between 1s Input : 00011 Output : VALID
In Set 1, we have discussed general approach for validity of string.In this post, we will discuss regular expression approach for same and it is simple.
As we know that in a string if there is zero between 1’s, than string is not valid.Hence below is one of the regular expression for invalid string pattern.
10+1
So here is the simple regex algorithm.
- Loop over the matcher(string)
- if above regex match is find in the matcher, then string is not valid, otherwise valid.
// Java regex program to check for valid string import java.util.regex.Matcher; import java.util.regex.Pattern; class GFG { // Method to check for valid string static boolean checkString(String str) { // regular expression for invalid string String regex = "10+1"; // compiling regex Pattern p = Pattern.compile(regex); // Matcher object Matcher m = p.matcher(str); // loop over matcher while(m.find()) { // if match found, // then string is invalid return false; } // if match doesn't found // then string is valid return true; } // Driver method public static void main (String[] args) { String str = "00011111111100000"; System.out.println(checkString(str) ? "VALID" : "NOT VALID"); } } |
Output:
VALID
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