N-Queens II

public int totalNQueens(int n) {
// Start typing your Java solution below
// DO NOT write main() function
if(n <= 0) return 0;
return totalNQueens(n, new int
, 0);
}

public int totalNQueens(int n, int[] queens, int index) {
if(index == n) return 1;
int sum = 0;
//means for the column
for(int i = 0; i < n; i++) {
boolean flag = true;
//means for the row
for(int j = 0; j < index; j++){
if(queens[j] == i || Math.abs(queens[j] - i) == index - j) {
flag = false;
break;
}
}
if(flag == true) {
queens[index] = i;
sum += totalNQueens(n, queens, index + 1);
}
}
return sum;
}