Off by one error again, your formula drops m from the answer. (And the obvious fix will need more cases if your range potentially includes negative integers.)

But still, you are essentially correct. After some wrapper logic, the problem really does boil down to being able to efficiently calculate the sum of the digits from 1 to n for any positive integer n.

In reply to Re (tilly) 3: Finding sum of all digits from 1 to 1 million. by tilly
in thread Finding sum of all digits from 1 to 1 million. by vladb

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