UVa 673 - Parentheses Balance

Parentheses Balance

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

(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

Miguel Revilla 
2000-08-14

#include <cstdio>
#include <iostream>
#include <cstring>
#include <stack>
using namespace std;
       
const int MAX = 150;

stack<char> s;
string buff;
int n;

bool find(char ch)
{
	if(s.empty())
		return false;

 	 if(ch==')')
 	 {
	  	if(s.top()=='(')
     	{
	     	s.pop();
		 	return true; 	  																			                                    
     	}
   	 	return false;		
	  }else if(ch==']'){
	  	if(s.top()=='[')
     	{
	     	s.pop();
		 	return true; 	  																			                                    
     	}
   	 	return false;	
	}     	 			
}

void solve()
{
	int length = buff.size();
	bool ans=true;                                        
	for(int i=0; i < length; i++)
	{
		if(buff[i]=='('
			|| buff[i]=='[')
			s.push(buff[i]);
		else 
		{
			if(!find(buff[i])){
				ans = false;
				break;
			}
		}
	}
	if(ans && s.empty())
         printf("Yes\n");
    else 
    	 printf("No\n");	
}
	
void init()
{
	while(!s.empty())
		s.pop();
}
					   
void read()
{

	cin>>n;
	cin.get();
	while(n--)
	{
		init();
		getline(cin, buff);
		solve();
	}
}

int main()
{
//  freopen("in.txt","r",stdin);
   
	
	read();

	return 0;
}

两点需要注意的地方，一个输入，一个在输出时需要判断栈是否为空，唉，贡献了好几个WA