How does only traversing till end of array guarantee that i’ll be able to reach the start of the circuit?

# Doubt in solution

As we know that the Total(Gas) >= Total(Cost) for soln. to exist, so while traversing, let us say that the index **j** gives **negative sum difference** value i.e.Total(Gas)<Total(Cost) (Total only till index **j**). Now, we start traversing again from index **j+1** making the previous totals (both Total(Gas) and Total(Cost)) as **0**, now let us assume that from index **j+1** to **end of array** we don’t find any **negative sum difference** value. What does that mean?

index --> 0 1 2 3 4…j j+1 j+2 … n-1

values–>(— **-ve** —) (---- **+ve** -----)

That means that **j+1** index is the soln., because even if we continue taking sum after index n-1 i.e. from 0 we are bound to get +ve value because the overall Total(Gas) >= Total(Cost) exist.

Hence, your answer.

If you want explaination of editorial or (kinda) proof of editorial solution