How to avoid nested loop in this program

Question

I want to make the program more efficient
import java.util.Scanner;
public class Program
{
public static void main(String[] args)
{
Scanner ob =new Scanner(System.in);
String s=ob.nextLine();
int c=0;
for(int i=0;i<s.length()-1;i++)
{
for(int j=(i+1);j<s.length();j++)
{
if(s.charAt(i)==s.charAt(j))
{
c++;break;
}
}

}
if(c>0)
System.out.println("Deja Vu");
else
System.out.println("Unique");

}
}

Answer 1

You can try to do this way. With boolean array. Pretty simple solution and you can avoid double for loop.

https://code.sololearn.com/c6iDFjEgbmTu/?ref=app