最原始的DFS算法为：

private static void getPath(List<Entry> list, ID id, ArrayList<Integer> matchPath,
int... path) {
  for (int i = 0; i < list.size(); i++) {
    int length = path.length;
    int[] currentPath = new int[length + 1];
    System.arraycopy(path, 0, currentPath, 0, length);
    currentPath[length] = i;

    Entry entry = list.get(i);
    if (id.equals(entry.id)) {
      if (matchPath.size() == 0) {
        for (int j : currentPath) {// clone
          matchPath.add(j);
        }
      }
    } else
       getPath(entry.getChildren(), id, matchPath, currentPath);
  }
}

但是这种算法虽然完成了任务，但总觉得过于罗嗦。写好后三个月，又摸回去改了改，结果如下，使用了Stack来和DFS互动。

private static void getPath(List<Entry> list, ID id, Stack<Integer> path, Flag isFound) {
  for (int i = 0; i < list.size() && !isFound.value; i++) {
    Entry entry = list.get(i);
    path.push(i);
    if (id.equals(entry.id)) {
      isFound.value = true;
      return;
    } else{
      getPath(entry.getChildren(), id, path, isFound);
    }
  }
  if(isFound.value)
    return;
  if ( !path.empty())
    path.pop();
}

简单的才是对的，要有这种信念。做人就得信，做….

to be continued