[leetcode/java] 617.Merge Two Binary Trees

/** 
 * Definition for a binary tree node. 
 * public class TreeNode { 
 *     int val; 
 *     TreeNode left; 
 *     TreeNode right; 
 *     TreeNode(int x) { val = x; } 
 * } 
 */ 
class Solution { 
    public TreeNode mergeTrees(TreeNode t1, TreeNode t2) { 
        return merge(t1, t2); 
    } 
     
    public TreeNode merge(TreeNode t1, TreeNode t2) { 
        if (t1 == null) return t2; 
        if (t2 == null) return t1; 
         
        t1.val += t2.val
        t1.left = merge(t1.left, t2.left); 
        t1.right = merge(t1.right, t2.right); 
         
        return t1; 
    } 
}