Balanced Brackets

A bracket is considered to be any one of the following characters: (, ), {, }, [, or ].

Two brackets are considered to be a matched pair if the an opening bracket (i.e., (, [, or {) occurs to the left of a closing bracket (i.e., ), ], or }) of the exact same type. There are three types of matched pairs of brackets: [], {}, and ().

A matching pair of brackets is not balanced if the set of brackets it encloses are not matched. For example, {[(])} is not balanced because the contents in between { and } are not balanced. The pair of square brackets encloses a single, unbalanced opening bracket, (, and the pair of parentheses encloses a single, unbalanced closing square bracket, ].

By this logic, we say a sequence of brackets is balanced if the following conditions are met:

• It contains no unmatched brackets.
• The subset of brackets enclosed within the confines of a matched pair of brackets is also a matched pair of brackets.

Given a strings of brackets, determine whether each sequence of brackets is balanced. If a string is balanced, return YES. Otherwise, return NO.

Function Description

Complete the function isBalanced in the editor below. It must return a string: YES if the sequence is balanced or NO if it is not.

isBalanced has the following parameter(s):

• s: a string of brackets

Input Format

The first line contains a single integer , the number of strings.
Each of the next  lines contains a single string , a sequence of brackets.

Solution In Java:

import java.io.*;
import java.math.*;
import java.security.*;
import java.text.*;
import java.util.*;
import java.util.concurrent.*;
import java.util.regex.*;

public class Solution {

    // Complete the isBalanced function below.
    static String isBalanced(String s) {
        String output ="NO";
        Stack<Character> balancer = new Stack<Character>();
        for(int i=0;i<s.length();i++) {
            if(s.charAt(i)=='(' || s.charAt(i)=='{' || s.charAt(i)=='[') {
                balancer.push(s.charAt(i));
            }else {
                char closed = s.charAt(i);
                if(!balancer.isEmpty()) {
                    char opened = balancer.pop();
                    boolean matched = matchChars(closed,opened);
                    if(!matched) {
                        return "NO";
                    }
                }else {
                    return "NO";
                }
            }
        }
        if(balancer.isEmpty()) {
            output = "YES";
        }
        return output;
    }
     private static boolean matchChars(char closed, char opened) {
        if(closed == ')' && opened == '(') {
            return true;
        }else if(closed == '}' && opened == '{') {
            return true;
        }else if(closed == ']' && opened == '[') {
            return true;
        }
        return false;
    }
    private static final Scanner scanner = new Scanner(System.in);

    public static void main(String[] args) throws IOException {
        BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter(System.getenv("OUTPUT_PATH")));

        int t = scanner.nextInt();
        scanner.skip("(\r\n|[\n\r\u2028\u2029\u0085])?");

        for (int tItr = 0; tItr < t; tItr++) {
            String s = scanner.nextLine();

            String result = isBalanced(s);

            bufferedWriter.write(result);
            bufferedWriter.newLine();
        }

        bufferedWriter.close();

        scanner.close();
    }
}