box-o-sand/curses-practice/JustForFun/queens.c

#include <stdio.h>
#include <curses.h>

#define QUEEN_CHAR '*'

int *nqueens(int num);
int place(int current, int *position);
int print(int *positions, int num_queens);
void board(WINDOW *win, int starty, int startx, int lines, int cols,
       int tile_width, int tile_height);

int main(int argc, char *argv[])
{
    int num_queens, *positions, count;

    if(argc != 2)
    {    printf("Usage: %s <number of queens (chess board order)>\n", argv[0]);
        exit(1);
    }

    num_queens = atoi(argv[1]);
    initscr();
    cbreak();
    keypad(stdscr, TRUE);
    positions = nqueens(num_queens);
    free(positions);
    endwin();
    return 0;
}

int *nqueens(int num)
{
    int current, *position, num_solutions = 0;

    position = (int *) calloc(num + 1, sizeof(int));

    position[1] = 0;
    current = 1;    /* current queen is being checked    */
                /* position[current] is the coloumn*/
    while(current > 0){
        position[current] += 1;
        while(position[current] <= num && !place(current, position) )
            position[current] += 1;
        if(position[current] <= num){
            if(current == num)    {
                ++num_solutions;
                print(position, num);
            }
            else {
                current += 1;
                position[current] = 0;
            }
        }
        else current -= 1;        /*    backtrack        */
    }
    printf("Total Number of Solutions : %d\n", num_solutions);
    return(position);
}

int place(int current, int *position)
{
    int i;
    if(current == 1) return(1);
    for(i = 1; i < current; ++i)
        if(position[i] == position[current]) return(0);
        else if(abs(position[i] - position[current]) ==
            abs(i - current))
            return(0);

    return(1);
}

int print(int *positions, int num_queens)
{    int count;
    int y = 2, x = 2, w = 4, h = 2;
    static int solution = 1;

    mvprintw(0, 0, "Solution No: %d", solution++);
    board(stdscr, y, x, num_queens, num_queens, w, h);
    for(count = 1; count <= num_queens; ++count)
    {    int tempy = y + (count - 1) * h + h / 2;
        int tempx = x + (positions[count] - 1) * w + w / 2;
        mvaddch(tempy, tempx, QUEEN_CHAR);
    }
    refresh();
    mvprintw(LINES - 2, 0, "Press Any Key to See next solution (F1 to Exit)");
    if(getch() == KEY_F(1))
    {    endwin();
        exit(0);
    }
    clear();
}

void board(WINDOW *win, int starty, int startx, int lines, int cols,
       int tile_width, int tile_height)
{    int endy, endx, i, j;

    endy = starty + lines * tile_height;
    endx = startx + cols  * tile_width;

    for(j = starty; j <= endy; j += tile_height)
        for(i = startx; i <= endx; ++i)
            mvwaddch(win, j, i, ACS_HLINE);
    for(i = startx; i <= endx; i += tile_width)
        for(j = starty; j <= endy; ++j)
            mvwaddch(win, j, i, ACS_VLINE);
    mvwaddch(win, starty, startx, ACS_ULCORNER);
    mvwaddch(win, endy, startx, ACS_LLCORNER);
    mvwaddch(win, starty, endx, ACS_URCORNER);
    mvwaddch(win,     endy, endx, ACS_LRCORNER);
    for(j = starty + tile_height; j <= endy - tile_height; j += tile_height)
    {    mvwaddch(win, j, startx, ACS_LTEE);
        mvwaddch(win, j, endx, ACS_RTEE);
        for(i = startx + tile_width; i <= endx - tile_width; i += tile_width)
            mvwaddch(win, j, i, ACS_PLUS);
    }
    for(i = startx + tile_width; i <= endx - tile_width; i += tile_width)
    {    mvwaddch(win, starty, i, ACS_TTEE);
        mvwaddch(win, endy, i, ACS_BTEE);
    }
    wrefresh(win);
}