smunix/digit-operations

let's combine digits to make numbers

digit-operations

Assuming you are given the list of all digits going from 1 to 9, 1 2 3 4 5 6 7 8 9. How many ways can we intercalate the operations multiplication (*) and addition (+) between the digits in such a way that the value of the arithmetic expression we get equals X (set X = 50 for example) ? Note that the order of the digits 1 to 9 has to be ordered from smallest to the greatest one.

Here’s one solution for X=50:   1+2+3*4+5+6+7+8+9 è 50

Here’s one solution for X=100: 12+34+5+67+8+9   è 100 [1]

As you can see in [1], 34 is also used as we didn’t put any operator between 3 and 4. So note that not putting any operation between digits is a valid choice as well.

I usually make up for combinations of this concept by asking the candidate to write code to print out all the solutions, or just print how many possible solutions we do have.

Next step is usually discussing the complexity of the provided solution by the candidate, but it’s not very important I believe (anyone knows why ?).

Happy coding !

=================