SudokusSolve is made for helping you solving Sudoku puzzles. You can let it solve single cells, rows, columns or 3x3 boxes, tell you where a number is in a row, column or box, or solve the puzzle as a whole. As SudokusSolve can also create Sudokus, you can also just use it as a simple Sudoku App that always tells you if you've made a mistake and helps you when you get stuck.
If you also want to be able to scan Sudokus from paper or an image in your photo library, try the full version Sudoku Scan&Solve
Have fun!