11881 - Internal Rate of Return

[rizar]

I spent half of contest time on solving it but have no ideas how to deal with precision problems.
It's clear that answer can't be "No", but how to distinguish case with two close roots from case with exactly one root?
Thanks in advance.

[Leonid]

Since CF(0) < 0 and CF(i) > 0 it can be proved that there is only 1 answer. Consider when IRR = -1, then the sum approaches infinity. On the other hand when IRR is approaching infinity, the answer is approaching 0.

I hope you are aware that there was a clarification during the contest specifying that the correct formula is (I + IRR)^k, and not (I + IRR^k). The problem description as it stands now is ambiguous, however there are two indicators that drive towards thinking that it should be (I + IRR)^k. Such as 1) Internal Rate of Return Wiki page and 2) mismatching second sample input.

[rizar]

Oh, unfortunately I didn't know correct formula There was no such clarification on "Clarification board" or maybe I searched in a wrong place. But looking IRR in wikipedia could be a great idea.
Thank you.

[rujialiu]

Sorry, I was not aware of this error during the contest. The wrong formula is resulted from to the quick generation of HTML from DOC.
Now the figure is corrected. Thanks for pointing it out!