错误：控制到达非无效 function [-Werror=return-type] C++ 错误的结尾

Question

I need help to solve this problem. I am getting an error which is given below and code is also given. This program is to find whether bracket is balanced or not .

#include <bits/stdc++.h>
#include<stack>
using namespace std;

// Complete the isBalanced function below.
string isBalanced(string s) {
    stack <char> st;
    for(auto c:s){
        switch (c){
            case '(':
            case '{':
            case '[':
                  st.push(c);
                   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;
            default: break;
        }
    }

}

int main()
{
    ofstream fout(getenv("OUTPUT_PATH"));
    
    int t;
    cin >> t;
    cin.ignore(numeric_limits<streamsize>::max(), '\n');
    
    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;
}




this is a program to check bracket is balanced or not.

this is the code I have written and it's throwing me the error. Please help me to fix this problem. I have tried by adding stack header file but still, I am getting same error.

***Solution.cpp: In function ‘std::__cxx11::string isBalanced(std::__cxx11::string)’:
 Solution.cpp:7:18: error: control reaches end of non-void function [-Werror=return-type]
    stack <char> st;
              ^~
 cc1plus: some warnings being treated as errors***

Answer 1

No return statement will executed in your isBalanced function when the for loop is completed without executing return statement inside that.

It seems you should add code to check if the stack st is empty and return proper things according to its result after the loop.