uva-673 Parentheses Balance

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

 这个题的意思是看一个表达示的括号是不是平衡的，空表达示也是平衡的，平衡就输出YES，否则输出NO。

解题思路：

1.如果表达示为空，输出YES。

2.利用一个栈，表达示从左到右扫描，遇到左括号入栈，右括号出栈，如果最后线空输出YES，否则输出NO。

 

#include <iostream>

#include<deque>

#include<algorithm>

#include<cstdio>

#include<stack>

#include<string>

using namespace std;

char f(char c)

{

    if(c==')')return '(';

    if(c==']')return '[';

    return 0;

}

bool judge(const string& s)

{

    stack<char>st;

    st.push('0');

    for(int i=0;i<s.size();i++)

    {

        if(st.top()!=f(s[i]))

        st.push(s[i]);

        else st.pop();

    }

    return st.size()==1;

}





int main()

{

    int n;

    cin>>n;

    string s;

    getchar();

    while(n--)

    {

        getline(cin,s);

        if(s.size()==0||judge(s))cout<<"Yes"<<endl;

        else cout<<"No"<<endl;

    }

    return 0;

}