226. Invert Binary Tree

Invert a binary tree (mirror it left to right) and return its root.

Visit nodes level by level and swap each node's children.

1function invertTree(root: TreeNode | null): TreeNode | null {
2  const queue = root ? [root] : [];
3  while (queue.length) {
4    const n = queue.shift()!;
5    [n.left, n.right] = [n.right, n.left];
6    if (n.left) queue.push(n.left);
7    if (n.right) queue.push(n.right);
8  }
9  return root;
10}

tree

queue

Queue the root.

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