import java.util.ArrayList;

import java.util.List;

/**

* Created by wangzhan on 2016-05-31.

*/

public class Solution {

public static void main(String[] args) {

TreeNode root = new TreeNode(3);

root.left = new TreeNode(9);

root.right = new TreeNode(20);

root.right.left = new TreeNode(15);

root.right.right = new TreeNode(7);

Solution instance = new Solution();

System.out.println(instance.binaryTreePaths(root));

}

public List<String> binaryTreePaths(TreeNode root) {

ArrayList<String> pathList = new ArrayList<>();

if (root == null)

return pathList;

String path = "";

childPaths(pathList, root, path);

return pathList;

}

private void childPaths(ArrayList<String> pathList, TreeNode root, String path) {

if (root == null)

return;

path += root.val;

if (root.left == null && root.right == null) {

pathList.add(path);

return;

} else {

childPaths(pathList, root.left, path+"->");

childPaths(pathList, root.right, path+"->");

}

}

}

class TreeNode {

int val;

TreeNode left;

TreeNode right;

public TreeNode(int val) {

this.val = val;

this.right = this.left = null;

}

}