package Task;

import java.util.LinkedList;
/*
 * simply stack (FILO) for char based on LinkedList<Character> functional..
 */
public class MyStack {
	MyStack(){
		list=new LinkedList<Character>();
	}

	/*
	 * throws IndexOutOfBoundsException of LinkedList..
	 */
	public Character pop() throws Exception{
		return list.remove(0);
	}

	public Character top() throws Exception{
		return list.getFirst();
	}

	public void push(Character c){
		list.addFirst(c);
	}

	public boolean isEmpty(){
		return 0==list.size();
	}

	/*
	 * @param String str - sequence [ { ( ) } ] and some all characters..
	 * Checking. is str it right bracket sequence?
	 */
	public static boolean isCorrect(String str){
		MyStack stack = new MyStack();
		for(int i=0;i<str.length();++i){
			Character cStr =str.charAt(i);
			//if bracket - opening..
			if((cStr=='(')||(cStr=='{')||(cStr=='[')){
				stack.push(cStr);
			}else if((cStr==')')||(cStr=='}')||(cStr==']')){
				//if bracket - closing.. (testing because it may be not bracket (but numbers or smt. ))
				Character cStack;
				try {
					cStack = stack.pop();
				} catch (Exception e) {
					//open bracket is less than closing
					return false;
				}
				//parsing gotten character
				switch(cStack){
				case '(':
					if(cStr!=')')
						//i hope that != correctly work with Character and i not required use equals...
						//ok, it works..
						return false;
					break;
				case '{':
					if(cStr!='}')
						return false;
					break;
				case '[':
					if(cStr!=']')
						return false;
					break;
				};
			}
		}

		if(stack.isEmpty())
			return true;
		else
			return false;
	}

	private LinkedList<Character> list;
}