Project Euler 79: what am I missing?

Question

Hi Guys,

I'm not interested in the answer, but I need to be pointed in the right direction

Here's problem 79

I first try to analyze the file myself. I've noticed that the number 7 only ever appears as the first digit.

This immediately implies that all the numbers containing 7 never overlaps with under numbers (on the left side).

Since the questions in project euler always have 1 answer, I believe I'm misunderstanding the question. Do I not have to use all numbers? If I do have to use all numbers, there's many different possible numbers.

Where am I going wrong?

Answer 1

I too did this one entirely by hand.

Your observation about 7 only appearing as the first digit is relevant; it means that no number ever comes before 7 -- or, in other words, that 7 is the first digit of the solution.

While they don't say how many digits you'll need, you can safely assume (to ensure a unique solution) that any digit not appearing in the file is not in the code you're looking for, and also that no digit appears twice in the code.

I hope that clears up the problem without taking you too far towards the solution.