Write a C++ program with the following instruction.

Make sure you comment or let the user what code you input.

1. Given four digits, find the maximum valid time that can be displayed on a digital clock (in 24-hour format) using those digits.

For example, given digits 1,8,3,2 the maximum valid time is "23:18". Note that "28:31" is not a valid time.

Write a function:

string MaxTime(int A, int B, int C, int D);

that, given four integers A,B,C,D, returns the maximum valid time in string format "HH:MM" or "NOT POSSIBLE" if it is not possible to display a valid time.

Examples: given 1,8,3,2, the function MaxTime shoud return "23:18".

Given 2,4,0,0 the funtion should return "20:40".

Given 3,0,7,0 the function should return "07:30"

Given 9,1,9,7 the function should return "NOT POSSIBLE". Since there is no possible valid time.

Assume that: A,B,C,D are integers with in the range [0..9]

In your solution, focus on correctness as well as the performance of your solution. Try to achieve O(n) if possible rather than O(n^2) solution.