题解 | #合并二叉树#

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 mergeTrees(TreeNode t1, TreeNode t2) {
        // write code here
        if (t1 == null)
            return t2;
        if (t2 == null)
            return t1;
        Merge(t1, t2);
        return t1;
    }

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