leetcode_071

public class  {
    public String simplifyPath(String path) {
        String[] strs = path.split("/");
        Stack<String> stack = new Stack<>();
        
        String back = "..";
        String cur = ".";
        
        for(String str : strs) {
            
            if(str.equals(back)){
                if(!stack.isEmpty()) {
                    stack.pop();    
                }
                continue;
            }
            // "." 或者 "" 不变
            if(str.equals(cur) || str.equals("")){
                continue;
            }
            // 其他路劲则是入栈
            stack.push(str);
        }
        
        if(stack.isEmpty()){
            return "/";
        } else {
            // 反转stack
            Stack<String> stack1 = new Stack<>();
            while(!stack.isEmpty()){
                stack1.push(stack.pop());
            }
            stack = stack1;
            
            // 此时栈顶为根目录
            StringBuilder sb = new StringBuilder("/");
            while(!stack.isEmpty()){
                sb.append(stack.pop());
                sb.append("/");
            }
            sb.deleteCharAt(sb.length()-1);
            return sb.toString();
        }   
    }
}