public class BracketsVerification {
	public static void main(String[] args) {
		// test cases
		System.out.println(isMatched(null)); // true
		System.out.println(isMatched("")); // true
		System.out.println(isMatched("()")); // true
		System.out.println(isMatched("()[]")); // true
		System.out.println(isMatched("(()[])")); // true
		System.out.println(isMatched("[[](()[])]()")); // true
		System.out.println(isMatched("[)")); // false
		System.out.println(isMatched(")")); // false
		System.out.println(isMatched(")(")); // false
		System.out.println(isMatched("[[]((()[])]())")); // false
	}

	public static boolean isMatched(String brackets) {
		if (brackets == null || brackets.isEmpty()) {
			return true;
		}
		String tracking = "";
		do {
			if (tracking.isEmpty() || !isMatched(brackets.charAt(brackets.length() - 1), tracking.charAt(0))) {
				tracking = brackets.charAt(brackets.length() - 1) + tracking;
			} else {
				tracking = tracking.substring(1);
			}
			brackets = brackets.substring(0, brackets.length() - 1);
		} while (!brackets.isEmpty());
		return tracking.isEmpty();
	}

	private static boolean isMatched(char a, char b) {
		return (a == '(' && b == ')') || (a == '[' && b == ']');
	}
}