https://itunes.apple.com/us/app/sudoku- ... ?ls=1&mt=8
I coded this last year, since both my partner and my boss are addicted to Sudoku and then the bug bit me. Didn't like the gimmicky interfaces though, and so this.
It's free and there are no ads.
If you do like it, you could do me a big favour by reviewing it on the App Store. And your feedback would be much appreciated.