import java.util.*;
/*
* public class TreeNode {
* int val = 0;
* TreeNode left = null;
* TreeNode right = null;
* }
*/
public class Solution {
/**
*
* @param t1 TreeNode类
* @param t2 TreeNode类
* @return TreeNode类
*/
public TreeNode preOrder(TreeNode t1, TreeNode t2){
if(t1 == null && t2 == null){
return null;
}
TreeNode root;
int val = 0;
if(t1 != null){
val += t1.val;
}
if(t2 != null){
val += t2.val;
}
root = new TreeNode(val);
if(t1 != null && t2 != null){
root.left = preOrder(t1.left,t2.left);
root.right = preOrder(t1.right,t2.right);
}else if(t1 == null){
root.left = preOrder(null,t2.left);
root.right = preOrder(null,t2.right);
}else{
root.left = preOrder(t1.left,null);
root.right = preOrder(t1.right,null);
}
return root;
}
public TreeNode mergeTrees (TreeNode t1, TreeNode t2) {
// write code here
return preOrder(t1,t2);
}
}