学步园

括号匹配
时间限制: 1000ms内存限制: 1000kB
描述
假设表达式中只包含三种括号：圆括号、方括号和花括号，它们可相互嵌套，如([{}])或({[][()]})等均为正确的格式,而{[]})}或{[()]或([]}均为不正确的格式.

输入一串括号
如果输入的右括号多余，输出:Extra right brackets
如果输入的左括号多余, 输出:Extra left brackets
如果输入的括号不匹配，输出:Brackets not match
如果输入的括号匹配，输出:Brackets match
输入
{{{{)))
输出
Brackets not match
样例输入
{([)]}
样例输出
Brackets not match
参考代码

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Stack;
public class Main {
	public static void main(String[] args) throws IOException {
		BufferedReader cin = new BufferedReader(new InputStreamReader(System.in));
		String s = cin.readLine();
		int kind = judge(s);
		switch(kind){
			case 0:
				System.out.println("Brackets match");
				break;
			case 1:
				System.out.println("Brackets not match");
				break;
			case 2:
				System.out.println("Extra left brackets");
				break;
			case 3:
				System.out.println("Extra right brackets");
				break;
		}
	}
	private static int judge(String s) {
		Stack<Character> stk = new Stack<Character>();
		for(int i = 0;i < s.length();++ i){
			char c = s.charAt(i);
			switch(c){
				case '{':
				case '[':
				case '(':
					stk.push(c);
					break;
				case '}':
					if(stk.isEmpty()){
						return 3;
					}
					if('{' != stk.lastElement())
						return 1;
					stk.pop();
					break;
				case ']':
					if(stk.isEmpty()){
						return 3;
					}
					if('[' != stk.lastElement())
						return 1;
					stk.pop();
					break;
				case ')':
					if(stk.isEmpty()){
						return 3;
					}
					if('(' != stk.lastElement())
						return 1;
					stk.pop();
					break;
			}
		}
		if(!stk.isEmpty()){
			return 2;
		}
		return 0;
	}
}