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solution.ts
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solution.ts
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/**
* Definition for a binary tree node.
* class TreeNode {
* val: number
* left: TreeNode | null
* right: TreeNode | null
* constructor(val?: number, left?: TreeNode | null, right?: TreeNode | null) {
* this.val = (val===undefined ? 0 : val)
* this.left = (left===undefined ? null : left)
* this.right = (right===undefined ? null : right)
* }
* }
*/
function upsideDownBinaryTree (root: TreeNode | null): TreeNode | null {
if (!root || !root.left) {
return root;
}
function flip (root:TreeNode, parent:TreeNode, parentRight:TreeNode|null) {
parent.left = null;
parent.right = null;
if (root.left) {
const newRoot = flip(root.left, root, root.right);
root.right = parent;
root.left = parentRight;
return newRoot;
} else {
root.left = parentRight;
root.right = parent;
return root;
}
}
return flip(root.left, root, root.right);
}