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) {
        Stack<Character> stack = new Stack<>();
        for (char c : s.toCharArray()) {
            if (c == '(' || c == '{' || c == '[')
                stack.push(c);
            else if (stack.isEmpty())
                return false;
            else {
                if (c == ')' && stack.peek() != '(')
                    return false;
                else if (c == '}' && stack.peek() != '{')
                    return false;
                else if (c == ']' && stack.peek() != '[')
                    return false;
                stack.pop();
            }
        }
        return stack.isEmpty();
    } 
}