617. 合并二叉树

package leetcode;

public class demo_617 {
    public TreeNode mergeTrees(TreeNode root1, TreeNode root2) {
        //root1为空，直接返回root2剩余部分
        if(root1==null) {return root2;}
        //root2为空，直接返回root1剩余部分
        if(root2==null) {return root1;}
        root1.val=root1.val+root2.val;
        //递归遍历左子树
        root1.left=mergeTrees(root1.left, root2.left);
        //递归遍历右子树
        root1.right=mergeTrees(root1.right, root2.right);
        return root1;
    }
    
}