使用stack对象处理带圆括号的表达式。

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

int main()
{
	stack<char> sstack;
	string str;

	cout << "please int string for str:" << endl;
	cin >> str;

	string::iterator iter = str.begin();
	while(iter != str.end())
	{
		if(*iter != ')')
			sstack.push(*iter);
		else
		{
			while(sstack.top() != '(' && !sstack.empty())
			{
				sstack.pop();
			}
			if(sstack.empty())
				cout << "parentheses are not matched" << endl;
			else 
			{
				sstack.pop();
				sstack.push('@');
			}

		}
		++iter;
	}

	while(sstack.empty() == false)
	{
		char value = sstack.top();
		cout << value << " ";
		sstack.pop();
	}

	return 0;
}

输入输出结果：