Balancing Symbols

symbols匹配问题

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

struct Node
{
	char data;
	Node*next;
};

struct LinkStack
{
	Node*top;
};

LinkStack*create()
{
	LinkStack*stack = new LinkStack;
	stack->top = NULL;
	return stack;
}

bool isEmpty(LinkStack*stack)
{
	return (stack->top == NULL);
}

void pop(LinkStack*stack)
{
	Node*p = stack->top;
	stack->top = stack->top->next;
	delete p;
}

void push(LinkStack*stack, char item)
{
	Node*p = new Node;
	p->data = item;
	p->next = stack->top;
	stack->top = p;
}

char Top(LinkStack*stack)
{
	return stack->top->data;
}

int main()
{
	int n;
	cin >> n;
	while (n-->0)
	{
		string s;
		cin >> s;
		LinkStack*stack = create();
		bool flag = true;
		int n = s.size();

		for (int i = 0; i < n; i++)
		{
			if (s[i] == '(' || s[i] == '[' || s[i] == '{')
				push(stack, s[i]);
			if (s[i] == ')')
			{
				if (!isEmpty(stack))
				{
					if (isEmpty(stack) && Top(stack) != '(')
					{
						flag = false;
						break;
					}
					else
					{
						pop(stack);
					}
				}
				else
				{
					flag = false;
					break;
				}
			}
			else if (s[i] == ']')
			{
				if (!isEmpty(stack))
				{
					if (Top(stack) != '[')
					{
						flag = false;
						break;
					}
					else
					{
						pop(stack);
					}
				}
				else
				{
					flag = false;
					break;
				}
			}
			else if (s[i] == '}')
			{
				if (!isEmpty(stack))
				{
					if (Top(stack) != '{')
					{
						flag = false;
						break;
					}
					else
					{
						pop(stack);
					}
				}
				else
				{
					flag = false;
					break;
				}
			}
		}
		if (!isEmpty(stack))
			flag = false;
		if (flag)
			cout << "Yes" << endl;
		if (!flag)
			cout << "No" << endl;

		delete stack;
	}
	return 0;
}