leetcode 20. 有效的括号

class Solution {
    public boolean isValid(String s) {
        if(s.length()==0){
            return true;
        }
        if(s.length()==1){
            return false;
        }
        Stack<Character> stack=new Stack<>();
        int i=0;
        stack.push(s.charAt(i));
        i++;
        while(i!=s.length()){
            char tmp = s.charAt(i);
            if(!stack.empty()){
                char peek = stack.peek();
                if((tmp == ‘)‘&&peek==‘(‘)||(tmp==‘]‘&&peek==‘[‘)||(tmp==‘}‘&&peek==‘{‘)){
                    stack.pop();
                    i++;
                    continue;
                }
            }
            stack.push(tmp);
            i++;
        }
        return stack.empty();
    }
}