Nesting.java

package lessons.stacksandqueues;

import java.util.Stack;

/**
 * Nesting
 * https://app.codility.com/programmers/lessons/7-stacks_and_queues/nesting/
 * Difficulty : Easy
 * Related Topics : Stacks and Queues
 *
 * created by cenkc on 4/26/2020
 */
public class Nesting {

    public static void main(String[] args) {
        String A = "())";

        Nesting nesting = new Nesting();
        System.out.println(nesting.solution(A));
    }

    public int solution(String S) {
        Stack stack = new Stack();
        for (int i = 0; i < S.length(); i++) {
            char currentChar = S.charAt(i);
            if (isOpeningChar(currentChar)) {
                stack.push(currentChar);
            } else {
                if (stack.size() == 0) {
                    return 0; // first char is closingChar and it's not good
                }
                if (isPaired((char) stack.peek(), currentChar)) {
                    stack.pop();
                    continue;
                } else {
                    return 0;
                }
            }
        }
        if (stack.empty()) {
            return 1;
        }
        return 0;
    }

    private boolean isPaired(char c1, char c2) {
        if (c1 == '(' && c2 == ')') return true;
        return false;
    }

    public boolean isOpeningChar(char c) {
        return c == '(';
    }
}