private int selectBalanceAction() { int diff = determineHeight(left) - determineHeight(right); int subdiff; if (diff < -1) // right subtree is too tall if ((determineHeight(right.left) - determineHeight(right.right)) < 0) // outer tall return 2; // outer subtree already taller else return 4; // inner subtree is the problem else if (diff > 1) // left subtree is too tall if ((determineHeight(left.left) - determineHeight(left.right)) > 0) // outer tall return 1; // outer subtree already taller else return 3; // inner subtree is the problem else return 0; // no rebalance necessary }