617. 合并二叉树

#leetcode/tree/traversal/sub-tree

617. 合并二叉树

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leading to the advanced question

Solution Tips

方案一: 递归

又是一道同时递归的题目

var mergeTrees = function(root1, root2) {
    // if (root1 === null && root2 === null) return null;
    // if (root1 === null) root1 = new TreeNode(0, null, null);
    // if (root2 === null) root2 = new TreeNode(0, null, null);

    if (root1 === null) return root2
    if (root2 === null) return root1

    root1.val += root2.val

    root1.left = mergeTrees(root1.left, root2.left);
    root1.right = mergeTrees(root1.right, root2.right);

    return root1;
};