0071. Simplify Path

class Solution {

//    public String simplifyPath(String path) {
//         ArrayList<String> arr = new ArrayList<>();
//         Set<String> skip = new HashSet<>(Arrays.asList("..",".",""));
//         // String[] all = path.split("/");
//         for (String dir : path.split("/")) {
//             if (dir.equals("..") && !arr.isEmpty()) arr.remove(arr.size() - 1);
//             else if (!skip.contains(dir)) arr.add(dir);
//         }
//         StringBuilder sb = new StringBuilder("");
//         for(String dir : arr)
//             sb.append("/" + dir);
//         return sb.length() == 0 ? "/" : sb.toString();
//     }

    public String simplifyPath(String path) {
        List<String> arr= new ArrayList<>();
        String[] all = path.split("/");
        for (String s: all) {
            if (s.equals("..")) {
                if (!arr.isEmpty()) {
                    arr.remove(arr.size() - 1);
                }
                else {
                    continue;
                }
            }
            else if (s.equals(".") || s.equals("")) {
                continue;
            }
            else {
                arr.add(s);
            }
        }
        StringBuilder sb = new StringBuilder("/");
        for (String s: arr) {
            sb.append(s);
            sb.append("/");
        }
        if (sb.length() >= 3) {
            sb.deleteCharAt(sb.length() - 1);
        }
        return sb.toString();
    }
}