题解 | 括号的匹配

#include<bits/stdc++.h>
using namespace std;

int to_num(char c){
	if(c == '{') return  4;
	if(c == '}') return -4;
	if(c == '[') return  3;
	if(c == ']') return -3;
	if(c == '(') return  2;
	if(c == ')') return -2;
	if(c == '<') return  1;
	if(c == '>') return -1;
	return 0;
}

int main(){
	int t;  cin >> t;
	while(t--){
		string s;  cin >> s;
		stack<int> st;
		
		if(s.size() % 2 != 0){
			cout << "NO" << endl;
			continue;
		}
		
		for(int i=0 ; i < s.size() ; i++){
			int num = to_num(s[i]);
			
			if(!st.empty()){
				if(abs(st.top()) < abs(num)){
					break;
				}
				if(st.top() + num == 0){
					st.pop();
					num = 0;
				}
			}
			
			if(num != 0) 
			st.push(num);
		}
		
		if(st.empty()) cout << "YES" << endl;
		else			cout << "NO" << endl;
	}
	return 0;
}