Question

Explain in detail what the code below does:

public class MyClass {

      public static void main(String args[]) {     

        System.out.println(isUniqueChars("something"));

      }

      public static boolean isUniqueChars(String str) {

            int checker = 0;                                                                                  

            for (int i = 0; i < str.length(); ++i) {

                        int val = str.charAt(i) - 'a';

                        if ((checker & (1 << val)) > 0) return false;

                        checker |= (1 << val);

            }

            return true;

   }

}

Answer 1

Answer:

This is the bitwise approach to check if the String str has all unique characters or not.

The approach is that, for every character in the string str,

a bit at an index is set inside the checker variable which is initially initialized to 0.

Example: If a is encountered inside the string, its index is considered as 0, b is considered as 1, c as 2 and so on.

Now, if a is encountered, 0th bit of the checker variable is checked using & operator. If it is already set, that means the character is being repeated, we return false directly.

Otherwise , we set the bit to 1 and proceed to next character.

This way, if no false is returned, true is returned at last.

PLEASE UPVOTE IF YOU FOUND THIS HELPFUL!