HackerRank•Jun 02, 2025

Balanced Brackets

Hazrat Ali

HackerRank

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  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.

isBalanced has the following parameter(s):

  • string s: a string of brackets

Returns

  • string: either YES or NO

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.

Constraints

  •  where  is the length of the sequence.
  • All chracters in the sequences ∈ { {, }, (, ), [, ] }.

Output Format

For each string, return YES or NO.

Sample Input

STDIN           Function
-----           --------
3               n = 3
{[()]}          first s = '{[()]}'
{[(])}          second s = '{[(])}'
{{[[(())]]}}    third s ='{{[[(())]]}}'

Sample Output

YES
NO
YES
 
Solution 
 
#include <bits/stdc++.h>

using namespace std;

string ltrim(const string &);
string rtrim(const string &);

/*
 * Complete the 'isBalanced' function below.
 *
 * The function is expected to return a STRING.
 * The function accepts STRING s as parameter.
 */

string isBalanced(string s) {
    stack<char> brackets;
    for (char& c : s) {
        if (c == '[' || c == '{' || c == '(')
            brackets.push(c);
        else {
         
            if (brackets.empty() || abs(brackets.top() - c) > 2) return "NO";
            else brackets.pop();
        }
    }
    if (brackets.empty()) return "YES";
    return "NO";
}

int main()
{
    ofstream fout(getenv("OUTPUT_PATH"));

    string t_temp;
    getline(cin, t_temp);

    int t = stoi(ltrim(rtrim(t_temp)));

    for (int t_itr = 0; t_itr < t; t_itr++) {
        string s;
        getline(cin, s);

        string result = isBalanced(s);

        fout << result << "\n";
    }

    fout.close();

    return 0;
}

string ltrim(const string &str) {
    string s(str);

    s.erase(
        s.begin(),
        find_if(s.begin(), s.end(), not1(ptr_fun<int, int>(isspace)))
    );

    return s;
}

string rtrim(const string &str) {
    string s(str);

    s.erase(
        find_if(s.rbegin(), s.rend(), not1(ptr_fun<int, int>(isspace))).base(),
        s.end()
    );

    return s;
}

Comments