i have schengen Visa category C i will be landing to Vienna and take a bus directly to Croatia on same day ,there is any problem with police border to enter first day to Croatia ?
You should be fine.
Although Croatia is not part of the Schengen zone (legally bound to join, but not yet), it does allow vistors holding a Schengen visa without the need of an additional visa. Days spent in Croatia do not count towards the Schengen 90/180 rule.
The Croatian Ministry of Foreign and European affairs tells us the following on their website (emphasis not mine):
Pursuant to the Government’s Decision, starting with 22 July 2014, the Republic of Croatia applies the Decision No 565/2014/EU. All third-country nationals who are holders of valid Schengen documents, as well as national visas and residence permits of Bulgaria, Cyprus, and Romania do not require an additional (Croatian) visa for Croatia.
Third-country nationals who are holders of:
- uniform visa (C) for two or multiple entries, valid for all Schengen Area Member States;
- visa with limited territorial validity (LTV visa), for two or multiple entries, issued to the holder of a travel document that is not recognised by one or more, but not all of the Schengen Area Member States, and which is valid for the territory of the Member States recognising the travel document;
- long-stay visa (D) for stays exceeding three months, issued by one of the Schengen Area Member State;
- residence permit issued by one of the Schengen Area Member State;
do not require a visa for transit or intended stays in the territory of Croatia not exceeding 90 days in any 180-day period.
This basically means that the Croatian visa policy is just like Schengen, but it's not Schengen.
Also, according to this website, travellers holding a dual-entry Schengen visa must have one unused entry if travelling to Croatia.
I myself crossed the Croatian border from Slovenia with my friends (all Dutch) in the summer of 2017, when diplomatic tensions regarding territorial waters were a bit on the high side. Border police did ask a few stern questions about the intention of our stay but aside from that we had little trouble crossing it. We're crossing the border from Hungary this summer, I'll update this answer if we run into any problems there.