Given a tree representing a basic mathematical expression, where:
- The number of children extending from any node is greater than or equal to 2.
- Each node could either be a mathematical operator or a real number.
- Each of the leaf nodes should be (no promises :-)) a real number - Hint : Handle error here....
- The mathematical operators come from the set (-, +, /, *)
- If a node is a mathematical operator, the operation should be evaluated left-to-right:
- So, if you have a subtraction node with 1, 2 and 3 you would evaluate as 1 - 2 - 3 = -4. Write a method that calculates the value of such a tree. Write a program that calculates the value of the tree. Assume your code is part of a production grade library, so exceptional cases should be handled accordingly.
NOTE
- Your implementation should use only standard library modules. Do not use a pre-existing graph library. Write your own tree implementation and traversal methods.
Some tips:
- Classes, inheritance and encapsulation are your friends
- Code readability >> subtle performance gains
- Unit tests
####MySQL Given the following tables :
| employees |
|---|
| name |
| id |
| salary |
| age |
| project_id | | project_name |
| employee_id | | project_id | | time_spent |
Write a select statement returning the following data ordered by project name:
- project name
- sum of all salaries of all employees on the project
- average age of all employees on the project
Bonus Points : What indexes would you add to make your query go faster.
Example result set:
| Project | Total | Avg |
|---|---|---|
| Mad Cash App | 500000 | 33 |
| Big Money App | 300000 | 35 |