https://www.hackerrank.com/contests/hourrank-6/challenges/bear-and-steady-gene/submissions/code/5410841

Bear and Steady Gene

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

public class Solution {

    public static void main(String[] args) throws FileNotFoundException {
        /* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution. */
    	//uncomment it when doing in Eclipse
    	//System.setIn(new FileInputStream(args[0]));
    	Scanner in = new Scanner(System.in);
    	int length = in.nextInt();
    	int maxEach = length/4;
    	in.nextLine();
    	String gene = in.nextLine();
    	
    	int counterG = 0, counterA=0, counterC=0, counterT = 0;    	
    	Stack<Character> left = new Stack<Character>();
    	Stack<Character> right = new Stack<Character>();
    	List<Integer> lengths = new ArrayList<Integer>();
    	
    	int i;
    	for (i=0; i<length; i++){
    		if (gene.charAt(i)=='G'){
    			counterG++;
    			left.add('G');
    		}
    		if (gene.charAt(i)=='A'){
    			counterA++;
    			left.add('A');
    		}
    		if (gene.charAt(i)=='C'){
    			counterC++;
    			left.add('C');
    		}
    		if (gene.charAt(i)=='T'){
    			counterT++;
    			left.add('T');
    		}
    		if (counterG > maxEach|| counterA > maxEach|| counterC > maxEach|| counterT > maxEach){
    			lengths.add(left.size()-1);
    			char removed = left.pop();
        		if (removed=='G'){
        			counterG--;
        		}
        		if (removed=='A'){
        			counterA--;
        		}
        		if (removed=='C'){
        			counterC--;
        		}
        		if (removed=='T'){
        			counterT--;
        		}    
    			break;
    		}
    	}
    	
    	int j=length-1;
    	while(j>0 && !left.isEmpty()){
    		if (gene.charAt(j)=='G'){
    			counterG++;
    			right.add('G');
    		}
    		if (gene.charAt(j)=='A'){
    			counterA++;
    			right.add('A');
    		}
    		if (gene.charAt(j)=='C'){
    			counterC++;
    			right.add('C');
    		}
    		if (gene.charAt(j)=='T'){
    			counterT++;
    			right.add('T');
    		}
    		while((counterG > maxEach|| counterA > maxEach|| counterC > maxEach|| counterT > maxEach)&&!left.isEmpty()){
    			int len = left.size() + right.size() - 1;
    			lengths.add(len);
    			char removed = left.pop();
        		if (removed=='G'){
        			counterG--;
        		}
        		if (removed=='A'){
        			counterA--;
        		}
        		if (removed=='C'){
        			counterC--;
        		}
        		if (removed=='T'){
        			counterT--;
        		}    		
    		}
    		j--;
    	}
    	int result = length - Collections.max(lengths);
    	System.out.println(result);
    	
    }
}