Hey all, I been reading through these forums for a long time but have
never posted. Well, I got a dillema. I have a program of the Eight
Queen's program and I have to make it work without recursion. I have to
use a stack instead. It's been buggin me for a week and I have no clue
how to start it. Do you guy think you can help me out?
Here is the recursive part of the program:
size_t continue_placement(Board &board, size_t num_queens, long
int &steps)
// Assumes that bd contains num_queens queens, and is shadowed
// accordingly.
// Returns the number of queens it could place.
// A -1 in a board position q will show that there is a queen on q.
{
// Entry 1: start
size_t n = board.size;
if (n == num_queens) return num_queens;
// Display the board after every 10000 recursive calls.
steps++;
if (0 == steps % 10000) {
cerr << steps << endl;
board.display(cerr);
}
size_t max_num_queens = num_queens;
Board::Position q(n); // = (0, 0)
// Entry 2: start the loop with a loop test.
while(q.is_legal()){
if (0 == board.get(q)) {
// add new queen
board.set(q, -1);
board.queen_shadow(q, 1);
size_t new_max =
continue_placement(board,num_queens+1, steps);
// Entry 3: return from recursive call
if (new_max > max_num_queens)
max_num_queens = new_max;
if (n == max_num_queens)
return max_num_queens;
else{
// remove the new queen
board.queen_shadow(q, -1);
board.set(q, 0);
}
}
// Entry 4: we jumped here if 0 != board.get(q).
q = q.next();
}
// Entry 5: get here if the loop test fails.
return max_num_queens;
}
--
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