题解 | #有效括号序列#

import java.util.*;

public class Solution {
    /**
     *
     * @param s string字符串
     * @return bool布尔型
     */
    public boolean isValid (String s) {
        // write code here
        Stack<Character> st =  new Stack<>();
        for (int i = 0; i < s.length(); i++) {
            char c  = s.charAt(i);
            switch (c) {
                case'(':
                case'[':
                case'{':
                    st.push(c);
                    break;
                case ')':
                    if (st.empty() || st.peek() != '(')  return false;
                    st.pop();
                    break;
                case ']':
                    if (st.empty() || st.peek() != '[') return false;
                    st.pop();
                    break;
                case '}':
                    if (st.empty() || st.peek() != '{') return false;
                    st.pop();
                    break;
            }
        }
        return st.empty();
    }
}