Problem A 栈

Description

 

You are given a string consisting of parentheses () and []. A string of this type is said to be correct:

(a)

if it is the empty string

(b)

if A and B are correct, AB is correct,

(c)

if A is correct, (A ) and [A ] is correct.

Write a program that takes a sequence of strings of this type and check their correctness. Your program can assume that the maximum string length is 128.

Input

The file contains a positive integer n and a sequence of n strings of parentheses () and [], one string a line.

Output

A sequence of Yes or No on the output file.

Sample Input

3
([])
(([()])))
([()[]()])()

Sample Output

Yes
No
Yes
分析：
这个括号配对问题很符合后进先出-栈的方法，遇到左括号时进栈，遇到右括号时将栈顶元素与之配对的括号出栈。

#include <iostream>
#include <stack>
using namespace std;
int main()
{
	int n;
	cin >> n;
	cin.get();
	while (n--)
	{
		stack<char>st_ch;
		int loge = 1;
		char c;
		while (cin.get(c) && c != '\n')
		{
			if (c == ')')
			{
				if (st_ch.empty())
					loge = 0;
				else if (st_ch.top() == '(')
					st_ch.pop();
				else
					loge = 0;
			}
			else if (c == ']')
			{
				if (st_ch.empty())
					loge = 0;
				else if (st_ch.top() == '[')
					st_ch.pop();
				else
					loge = 0;
			}
			else
				st_ch.push(c);
		}
		if (st_ch.empty()&&loge)
			cout << "Yes" << endl;
		else
			cout << "No" << endl;

	}
	return 0;

}