1. public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
    2.         List<TreeNode> path_p = getPath(root, p);
    3.         List<TreeNode> path_q = getPath(root, q);
    5.         TreeNode ancestor = null;
    6.         for (int i = 0; i < path_p.size() && i < path_q.size(); i++) {
    7.             if (path_p.get(i) == path_q.get(i)) {
    8.                 ancestor = path_p.get(i);
    9.             } else {
    10.                 break;
    11.             }
    12.         }
    13.         return ancestor;
    14.     }
    16.     public List<TreeNode> getPath(TreeNode root, TreeNode target) {
    17.         List<TreeNode> path = new ArrayList<TreeNode>();
    19.         TreeNode node = root;
    21.         while (node != target) {
    22.             path.add(node);
    23.             if (target.val < node.val) {
    24.                 node = node.left;
    25.             } else {
    26.                 node = node.right;
    27.             }
    28.         }
    29.         path.add(node);
    30.         return path;
    31.     }