JAVA lab project.

Написать решения для 4ех заданий..

1. Write rotateWithLeftChild, which takes an avlNode, and rotate with its Left Child, update the height and return the new node.

2. Write a function called isAVLtree that check whether current Binary Search Tree is an AVLTree. Assume the current Tree is already a valid Binary Search Tree.

3. Write a function called printByFrequency to print all given input names in the list, grouped by number of times each name appears in the list. The runtime must be O(nlogn) where n is the number of names. All names with the same number of appearance (frequency) should be printed on the same line alphabetically separated by a comma, and names with more appearance should be printed first. The runtime must be O(nlogn) where n is the number of names in the list. It prints out names only. You may use following map to store the string to be printed on the same line. Note: Choose the appropriate map class. Add names should be efficient, if use a single String to store more than one name may slow down the runtime (but a StringBuilder is fine).

4. Write a function called sumZero that takes and array of integers, then check whether there’re two distinct numbers in the array to sum to zero, if so, return the index of first number. If not, return -1. The expected runtime must be O(n) where n is the array length.