题解 | #合并二叉树#

import java.util.*;

/*
 * public class TreeNode {
 *   int val = 0;
 *   TreeNode left = null;
 *   TreeNode right = null;
 *   public TreeNode(int val) {
 *     this.val = val;
 *   }
 * }
 */

public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param t1 TreeNode类 
     * @param t2 TreeNode类 
     * @return TreeNode类
     */
    public TreeNode mergeTrees (TreeNode t1, TreeNode t2) {
        // write code here
	  //使用前序遍历来访问
        if(t1==null) return t2;
        if(t2==null) return t1;
        TreeNode head = new TreeNode(t1.val+t2.val);
        head.left=mergeTrees(t1.left,t2.left);//注意这里的返回值
        head.right=mergeTrees(t1.right,t2.right);
        return head;
    }
}