LC617 树遍历

TreeNode* mergeTrees(TreeNode* root1, TreeNode* root2) {
    if(root1==nullptr){
        return root2;
    }else if(root2==nullptr){
        return root1;
    }

    TreeNode* root=new TreeNode(root1->val + root2->val);
    root->left=mergeTrees(root1->left,root2->left);
    root->right=mergeTrees(root1->right,root2->right);
    return root;
}