Check for balanced parentheses in an expression

balancedparanthesis.cpp

#include<iostream>
#include<stack>
using namespace std;

bool checkbalance(string expr)
{
	stack<char> s;
	char x;
	for(int i=0;i<expr.length();i++)
	{
		if(expr[i]=='(' || expr[i] == '{' || expr[i] == '[')
		{
			s.push(expr[i]);
		}
		if(s.empty())
		{
			return false;
		}
		switch(expr[i])
		{
			case ')':
				x=s.top();
				s.pop();
				if(expr[i]== '}' || expr[i] == ']')
				{
					return false;
				}
				break;
			case '}':
				x=s.top();
				s.pop();
				if(expr[i]== ')' || expr[i] == ']')
				{
					return false;
				}
				break;
			case ']' :
				x=s.top();
				s.pop();
				if(expr[i]== '}' || expr[i] == ')')
				{
					return false;
				}
				break;
		}
	}
	return (s.empty());
}

int main()
{
	string expr;
	cout<<"Enter Expression : ";
	cin>>expr;
	if(checkbalance(expr))
	{
		cout<<"Balanced!";
	}
	else
	{
		cout<<" Not Balanced!";
	}
	return 0;
}