華為筆試-括号比對

題目描述：

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

void func(const string str)
{
	stack<char> cstack;
	for (int i = 0; i < str.size(); ++i)
	{
		if (str[i] == '{' || str[i] == '[' || str[i] == '(')
		{
			cstack.push(str[i]);
		}

		if (str[i] == ')')
		{
			if (!cstack.empty() &&  cstack.top() == '(')
				cstack.pop();
			else
			{
				cout << "false" << endl;
				return;
			}
		}
		else if ( str[i] == ']')
		{
			if (!cstack.empty() && cstack.top() == '[')
				cstack.pop();
			else
			{
				cout << "false" << endl;
				return;
			}
		}
		else if (str[i] == '}')
		{
			if (!cstack.empty() && cstack.top() == '{')
				cstack.pop();
			else
			{
				cout << "false" << endl;
				return;
			}
		}
	}

	if (cstack.empty())
		cout << "true" << endl;
	else
		cout << "false" << endl;
}

int main()
{
	string str;
	while (cin >> str)
	{
		func(str);
	}

	return 0;
}