z-sudoku

Little Z. is an expert for solving Sudoku. One time Vanja was visiting him and looked was very confused with what Mr. Little Z. was doing with this number game. Vanja asked Little Z. to teach him how to solve Sudoku puzzles, and the first step was to teach Vanja which of the Sudoku puzzes that Z. has already solved have a correct solution.

Sudoku is a game in which we have to fill out 9 different characters into a 9x9 mesh, with the following rules.:
• Every character has to be used exactly 9 times.
• There can not be 2 same characters in a single row.
• There can not be 2 same characters in a single column.
• There can not be 2 same characters in any of the 3x3 sub-squares (as shown on the figure below).

+-----+-----+-----+
|6 9 2|7 1 5|4 8 3|
|1 5 3|4 2 8|7 9 6|
|8 4 7|9 3 6|2 5 1|
+-----+-----+-----+
|2 8 5|3 6 1|9 7 4|
|3 7 4|5 8 9|6 1 2|
|9 6 1|2 7 4|5 3 8|
+-----+-----+-----+
|5 3 9|8 4 2|1 6 7|
|4 1 8|6 9 7|3 2 5|
|7 2 6|1 5 3|8 4 9|
+-----+-----+-----+


Help Vanja to determine if the Little Z's solutions are correct