4.21 Write the remaining procedures to implement AVL single rotations.

Single rotation: Case 1 void rotateWithLeftChild( AvlNode * & k2 ) const { AvlNode *k1 = k2->left; k2->left = k1->right; k1->right = k2; k2->height = max( height( k2->left ), height( k2->right ) ) + 1; k1->height = max( height( k1->left ), k2->height ) + 1; k2 = k1; }