First line contains a single integer N. Next N lines contains N integers each, where jth integer int ith line denotes the value at ith row and jth column in sudoku grid. This value is 0, if the cell is empty.
I have not understood the meaning of the input format correcty
So if you are familiar with a sudoku puzzle, you know that it is a 9x9 grid. The input format is basically saying that you will be given N first, which will always be 9. Then i will represent rows and j represents columns. So, jth value in ith line means the arr[i][j] value. So you will be given a matrix where i=9 and j=9 and you have to simply take input like you take input for any 2D array or matrix.
If the value of a cell is 0, it means that that cell is not filled and you have to find its value. If there is a non-zero value at a cell, it means that that cell’s value is already given to you, just like in any sudoku puzzle, some values are given for you to start solving.