The Sep-2019 DMC Challenge “CrackTheCode” is a simple puzzle. We need to crack a 3 digit code based on these hints:

682 – one number is correct and in the correct position
645 – one number is correct but in the wrong position
206 – two numbers are correct but in the wrong positions
738 – nothing is correct
780 – one number is correct but in the wrong position.

It is easy to solve it using common sense in Sudoku-like style by removing impossible numbers as we consider all constraints one by one.  But after looking at the solution provided by Alex Fleischer who applied IBM CPLEX, I could not resist a temptation to do it with a free open-sourced JavaSolver. Here is my solution:

Here are the execution results: