static boolean solve(int numQueens, int whichCol) {
// Bottom-out condition 1:
if (numQueens == 0) {
// None to assign - done.
return true;
}
// Bottom-out condition 2:
if (whichCol >= board.size()) {
// No columns left to try: done.
return false;
}
// Try every un-forbidden spot in each row.
for (int row = 0; row < board.size(); row++) {
if (!board.isForbidden(row, whichCol)) {
// Try this location.
board.addQueen(row, whichCol);
boolean solutionExists = solve(numQueens - 1, whichCol + 1);
if (solutionExists) {
return true;
}
// Else, un-do
board.removeQueen(row, whichCol);
}
}
// Couldn't find a solution.
return false;
}
