public class Main
{
public static Boolean isItSaafe(Boolean board[][] , int row , int col){
int r = row-1 ;
int c = col ;
//vertically Upward
while(r >= 0){
if(board[r][c]){
return false ;
}
r-- ;
}
//horizontally left
r = row ;
c = col -1 ;
while(c >= 0){
if(board[r][c]){
return false ;
}
c--;
}
//vertically left
r = row -1 ;
c = col -1 ;
while(r >= 0 && c >= 0){
if(board[r][c]){
return false ;
}
r-- ;
c-- ;
}
// vertically right
r = row -1 ;
col = col +1 ;
while(r >= 0 && c <= board[0].length)
{
if(board[r][c]){
return false ;
}
r-- ;
c++ ;
}
return true ;
}
public static void Nqueen_2(Boolean board[][] , int row , int tq , int qpsf , String ans){
if(tq == qpsf)
{
System.out.println(ans);
return ;
}
if(row == board.length)
return ;
for(int i = 0 ; i < board[0].length ; i++){
//placed
if(isItSaafe(board ,row , i)){
board[row][i] = true ;
Nqueen_2(board , row+1 , tq , qpsf+1 , ans + "{"+ row + "-" + i + "}");
board[row][i] = false ;
}
}
//Not Placed
Nqueen_2(board , row+1 , tq , qpsf , ans);
}
public static void main(String[] args) {
Boolean board[][] = new Boolean[4][4];
Nqueen_2(board ,0 , 3 , 0 , "");
}
}
Sir , Please review my code i am getting a null pointer exception and i cant figure out the issue
Error :-
Exception in thread “main” java.lang.NullPointerException
at Main.isItSaafe(Main.java:12)
at Main.Nqueen_2(Main.java:69)
at Main.Nqueen_2(Main.java:71)
at Main.main(Main.java:81)