Parentheses Balance

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
 這個題的意思是看一個表達示的括號是不是平衡的，空表達示也是平衡的，平衡就輸出YES，否則輸出NO。自己寫完過了，細節沒優化。

#include<iostream>
#include<stack>
#include<cstring>
#include<string>
#include<cstdio>
using namespace std;
int main() {
	string op;
	stack<char> sp;
	int n;
	cin>>n;
	getchar();//吃掉輸入數字後的回車 
	while(n--) {
		int flag=1;
		while(!sp.empty()) sp.pop();
		getline(cin,op);
		for(int i=0; i<op.size(); i++) {
			if(op[i]=='('||op[i]=='[') sp.push(op[i]);
			else {
				if(op[i]==')') {
					if(sp.empty()) sp.push(op[i]); 
					if(sp.top()!='(') {
						cout<<"No"<<endl;
						flag=0;
						break;
					} else {
						sp.pop();
					}
				} else if(op[i]==']') {
					if(sp.empty()) sp.push(op[i]);
					if(sp.top()!='[') {
						cout<<"No"<<endl;
						flag=0;
						break;
					} else {
						sp.pop();
					}
				}
			}
		}
		if(sp.size()==0) cout<<"Yes"<<endl;
		else if(flag&&sp.size()) cout<<"No"<<endl;
	}
	return 0;
}