Binary Tree Paths

Given a binary tree, return all root-to-leaf paths.

For example, given the following binary tree:

1
 /   \
2     3
 \
  5

All root-to-leaf paths are:

["1->2->5", "1->3"]

public class Solution {
    public List<String> binaryTreePaths(TreeNode root) {
	    List<String> answer = new ArrayList<String>();
	    if (root != null) searchBT(root, "", answer);
	    return answer;
	}
	private void searchBT(TreeNode root, String path, List<String> answer) {
	    if (root.left == null && root.right == null) answer.add(path + root.val);
	    if (root.left != null) searchBT(root.left, path + root.val + "->", answer);
	    if (root.right != null) searchBT(root.right, path + root.val + "->", answer);
	}
}