C programming - Sodoku Solution using Backtracking

---------------------------------------------------

write a program that receives from the user sodoku board dimenstion(N) (can be any number for example: 3,4,5...)

and after that the sodoku board (we can fill elemnt a[i][j] with numbers from 1 to N and if it doesn't flled with a number then it is 0). after this the program must check if the board has solution then to print it, if not to print (NO solution!).

the rules: 1) to fill the board with numbers from 1 to N 2) two identical numbers must not appear on the same row

3) two identical numbers must not appear on the same colum

4) for this solution there is no limit for two identical numbers appearing in the same sub matrix(block) (for example: id it is 9x9 sodoku then number 1 for example can appear more than once in the sub matrix 3*3)

5)the programm must be effective to finish in few seconds *please run the program before giving me the solution.