balanced_brackets.cpp

#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> st;
    //int top = -1;
    for(int i = 0; i < s.size(); i++) {
        switch(s[i]) {
            case '(':
            case '[':
            case '{':
                st.push(s[i]);
                break;
                
            case ')': if (st.empty() || (st.top() != '('))
                            return "NO";
                      st.pop();
                      break;
                      
            case ']': if (st.empty() || (st.top() != '['))
                            return "NO";
                      st.pop();
                      break;
                      
            case '}': if (st.empty() || (st.top() != '{'))
                            return "NO";
                      st.pop();
                      break;
        }
    }
    return (st.empty()) ? "YES" : "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;
}