题解 | 有效括号序列

import java.util.*;


public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     *
     * @param s string字符串
     * @return bool布尔型
     */
    public boolean equalReverse(char s1, char s2) {
        return s1 == '[' && s2 == ']'
               || s1 == '{' && s2 == '}'
               || s1 == '(' && s2 == ')';
    }
    public boolean isValid (String s) {
        Stack<Character> st = new Stack<>();
        for (int i=0;i<s.length();++i) {
            char c = s.charAt(i);
            if (st.empty()) {
                st.push(c);
            } else {
                if (equalReverse(st.peek(), c)){
                    st.pop();
                }else{
                    st.push(c);
                }
            }
        }
        return st.empty();
    }
}