/*
C++ Program to check for balanced parentheses in an expression using stack.
Given an expression as string comprising of opening and closing characters
of parentheses - (), curly braces - {} and square brackets - [], we need to
check whether symbols are balanced or not.
*/
#include<iostream>
#include<stack>
#include<string>
using namespace std;
// Function to check whether two characters are opening
// and closing of same type.
bool ArePair(char opening,char closing)
{
if(opening == '(' && closing == ')') return true;
else if(opening == '{' && closing == '}') return true;
else if(opening == '[' && closing == ']') return true;
return false;
}
bool AreParanthesesBalanced(string exp)
{
stack<char> S;
for(int i =0;i<exp.length();i++)
{
if(exp[i] == '(' || exp[i] == '{' || exp[i] == '[')
S.push(exp[i]);
else if(exp[i] == ')' || exp[i] == '}' || exp[i] == ']')
{
if(S.empty() || !ArePair(S.top(),exp[i]))
return false;
else
S.pop();
}
}
return S.empty() ? true:false;
}
int main()
{
/*Code to test the function AreParanthesesBalanced*/
string expression;
cout<<"Enter an expression: "; // input expression from STDIN/Console
cin>>expression;
if(AreParanthesesBalanced(expression))
cout<<"Balanced\n";
else
cout<<"Not Balanced\n";
}
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