11.4.树的旋转

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11.4树的旋转

  The formal definition of rotation is:

  • rotateLeft(G): Let x be the right child of G. Make G the new left child of x.

  • rotateRight(G): Let x be the left child of G. Make G the new right child of x.

  As in the picture, it means:

  • RotateLeft(G): G moves left, promote its right child in the only natural way.(Promoting P means P is the new parent of G.)
  • RotateRight(P): P moves right, promote its left child in the only natural way.

  We can implement these operations by following codes: 

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private Node rotateLeft(Node h) {
    // assert (h != null) && isRed(h.left);
    Node x = h.left;
    h.left = x.right;
    x.right = h;
    return x;
}

// make a right-leaning link lean to the left
private Node rotateLeft(Node h) {
    // assert (h != null) && isRed(h.right);
    Node x = h.right;
    h.right = x.left;
    x.left = h;
    return x;
}