Sudoku solver problem

#1

In the given code Prateek sir wrote,in the canPlace function for row and column check,if we check for number present in that row or not and iterate over it we should always get false,Because the number which we are trying to check is itself present in the row.Am i correct or there is something else going in the code.please help

#2

You have to check if a no is already present in a row or not, if a no is already present in a column or not, and if a no is already present in a subarray small box or not, and based on tht you have to build your code.