How do i resolve the timeout issue?

Question

I am trying to execute this code but it shows the timeout error while the same logic if I applies with the c++ then is executes perfectly.

Can anyone help me out??

public static void main(String[] args) {

    Scanner sc = new Scanner(System.in);
    Stack<String> s = new Stack<>();
    int q = sc.nextInt();
    int n;
    String str = "";
    s.push(str);
    while (q != 0) {
        n = sc.nextInt();
        if (n == 1) {
            str += sc.nextLine().trim();

            s.push(str);
        } else if (n == 2) {
            str = str.substring(0, str.length() - sc.nextInt());
            s.push(str);
        } else if (n == 3) {
            System.out.println(str.charAt(sc.nextInt() - 1));
        } else {
            s.pop();
            str = s.peek();
        }
        q--;
    }

}

Answer 1

I am trying to execute this code but it shows the timeout error while the same logic if I applies with the c++ then is executes perfectly.

Can anyone help me out??

public static void main(String[] args) {

    Scanner sc = new Scanner(System.in);
    Stack<String> s = new Stack<>();
    int q = sc.nextInt();
    int n;
    String str = "";
    s.push(str);
    while (q != 0) {
        n = sc.nextInt();
        if (n == 1) {
            str += sc.nextLine().trim();

            s.push(str);
        } else if (n == 2) {
            str = str.substring(0, str.length() - sc.nextInt());
            s.push(str);
        } else if (n == 3) {
            System.out.println(str.charAt(sc.nextInt() - 1));
        } else {
            s.pop();
            str = s.peek();
        }
        q--;
    }

}