题解 | #括号序列#

JAVA

import java.util.*;
//用栈

public class Solution {
    /**
     * 
     * @param s string字符串 
     * @return bool布尔型
     */
    public boolean isValid (String s) {
        // write code here
        //判断偶数
        if(s.length() %2 != 0) return false;
        Stack<Character> stack = new Stack<Character>();
        //左侧括号入栈
        for(int i=0; i<s.length(); i++){
            if(s.charAt(i) == '(' || s.charAt(i) == '{' || s.charAt(i) == '['){
                stack.push(s.charAt(i));
            //依次和下面字符比较 如果遇到右侧括号就出栈
            }else if(!stack.isEmpty() && s.charAt(i)== ')' && stack.peek() == '('){
                stack.pop();
            }else if(!stack.isEmpty() && s.charAt(i)== ']' && stack.peek() == '['){
                stack.pop();
            }else if(!stack.isEmpty() && s.charAt(i)== '}' && stack.peek() == '{'){
                stack.pop();
            }
        }
        //判断是否为空。
        return stack.isEmpty();
    }
}