673

简单的题目，模拟栈的输入和输出操作，有两个点容易忽略：第一，字符串当中可能存在空格，这个要注意；第二，空串也是合法的输入。具体实现见如下代码：

#include<iostream>#include<vector>#include<string>#include<set>#include<stack>#include<queue>#include<map>#include<algorithm>#include<cmath>#include<iomanip>#include<cstring>#include<sstream>#include<cstdio>using namespace std;int n;int main(){cin >> n;string del;getline(cin,del);while (n--){string s;getline(cin, s);if (s.empty()){cout << "Yes" << endl;continue;}stack<char> st;bool flag = true;for (int i = 0; i < s.size(); i++){if (s[i] == ' ') continue;if (s[i] == '('||s[i]=='['){st.push(s[i]);}else if (s[i] == ')'){if (st.empty() || st.top() != '('){flag = false;break;}else st.pop();}else{if (st.empty() || st.top() != '['){flag = false;break;}else st.pop();}}if (!flag){cout << "No" << endl;}else{if (st.empty()) cout << "Yes" << endl;else cout << "No" << endl;}}return 0;}