Filter Users by Max Price and Return Unique Names

You are given an array of user objects, where each user has three properties:

• id (an integer)
• name (a string)
• price (an integer)

Write a function filterUsers(users, maxPrice) that:

1. Keeps only the users whose price is less than or equal to maxPrice.
2. From the filtered users, extracts the name property.
3. Returns an array containing only the unique names, preserving the order in which the names first appear in the filtered list.

If no user satisfies the price condition, the function should return an empty array.

Example

const users = [
  {id: 1, name: "Alice", price: 150},
  {id: 2, name: "Bob", price: 80},
  {id: 3, name: "Alice", price: 70},
  {id: 4, name: "Charlie", price: 200}
];
filterUsers(users, 100); // returns ["Bob", "Alice"]

Explanation: Only Bob (price 80) and the second Alice (price 70) are ≤ 100. The first Alice is excluded because her price is 150. The resulting names are "Bob" then "Alice", and both are unique.

Your solution should run in O(n) time where n is the number of users.