Help me in solving DNASTORAGE problem

help
,
1

My issue

what are the problem in my code

My code

/* package codechef; // don't place package name! */

import java.util.*;
import java.lang.*;
import java.io.*;

/* Name of the class has to be "Main" only if the class is public. */
class Codechef
{
	public static void main (String[] args) throws java.lang.Exception
	{
		// your code goes here
		Scanner s = new Scanner(System.in);
		int t = s.nextInt();
		while(t-- > 0){
		    int n = s.nextInt();
		    String sc = s.next();
		    String result = "";
		    for(int i = 0;i < n;i+=2){
		        if(sc.charAt[i] == '0' && sc.charAt[i + 1] == '0'){
		            result +="A";
		        }
		        else if(sc.charAt[i] == '0' && sc.charAt[i + 1] == '1'){
		            result += "T";
		        }
		        else if(sc.charAt[i] == '1' && sc.charAt[i + 1] == '0'){
		            result += "C";
		        }
		        else{
		            result += "G";
		        }
		    }
		    System.out.println(result);
		}
	}
}

Learning course: Strings using Java
Problem Link: CodeChef: Practical coding for everyone

2

@sushilp
just a little mistake.
i have corrected it in your code.

import java.util.*;
import java.lang.*;
import java.io.*;

/* Name of the class has to be "Main" only if the class is public. */
class Codechef
{
	public static void main (String[] args) throws java.lang.Exception
	{
		// your code goes here
		Scanner s = new Scanner(System.in);
		int t = s.nextInt();
		while(t-- > 0){
		    int n = s.nextInt();
		    String sc = s.next();
		    String result = "";
		    for(int i = 0;i < n;i+=2){
		        if(sc.charAt(i) == '0' && sc.charAt(i + 1) == '0'){
		            result +="A";
		        }
		        else if(sc.charAt(i) == '0' && sc.charAt(i + 1) == '1'){
		            result += "T";
		        }
		        else if(sc.charAt(i) == '1' && sc.charAt(i + 1) == '0'){
		            result += "C";
		        }
		        else{
		            result += "G";
		        }
		    }
		    System.out.println(result);
		}
	}
}