题解 | #括号序列#

比较好理解的方式，直观按照题意结题：

public boolean isValid (String s) {
    // write code here
    // 奇数一定不合法
    int len = s.length();
    if((len & 1) == 1) return false;
    Deque<Character> stack = new ArrayDeque<>();
    for (int i = 0; i < len; i++) {
        char cur = s.charAt(i);
        if(cur == '(' || cur == '{' || cur == '['){
            stack.push(cur);
        }else{
            if(stack.isEmpty()) return false;
            char top = stack.peek();
            if(cur == ')' && top == '('){
                stack.pop();
            }else if(cur == '}' && top == '{'){
                stack.pop();
            }else if(cur == ']' && top == '['){
                stack.pop();
            }else{
                return false;
            }
        }
    }
    return stack.isEmpty();
}