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
        if (t1 != null && t2 != null) {
            t1.val = t1.val + t2.val;
            if(t1.left != null && t2.left != null){
                travel(t1.left, t2.left);
            }else if(t2.left != null){
                t1.left = t2.left;
            }

            if(t1.right != null && t2.right != null){
                travel(t1.right, t2.right);
            }else if(t2.right != null){
                t1.right = t2.right;
            }
        } else if (t1 != null) {
            return t1;
        } else if (t2 != null) {
            return t2;
        }
        return t1;
    }
    public void travel(TreeNode t1, TreeNode t2) {
        if (t1 != null && t2 != null) {
            t1.val = t1.val + t2.val;
            if (t1.left != null && t2.left != null) {
                travel(t1.left, t2.left);
            } else if (t2.left != null) {
                t1.left = t2.left;
            }

            if (t1.right != null && t2.right != null) {
                travel(t1.right, t2.right);
            } else if (t2.right != null) {
                t1.right = t2.right;
            }
        } else if (t2 != null) {
            t1 = t2;
        }
        return;
    }
}