题解 | #合并二叉树#

好理解的简单方法，递归；

/*
 * 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 mergeTrees (TreeNode t1, TreeNode t2) {
        if(t1==null&&t2==null){
            return null;
        }
        else if(t1==null){
            t1=new TreeNode(t2.val);
        }
        else if(t2==null){
            t2=new TreeNode(t1.val);
        }
        else{
            t1.val=t1.val+t2.val;
            t2.val=t1.val+t2.val;
        }
       t1.left= mergeTrees ( t1.left, t2.left);
       t1.right=mergeTrees ( t1.right, t2.right);
        return t1;
        
        }

    }