问题
I'm trying to implement the N*N
queen algorithm with a little twist to it. In this version the queen can also move like a knight...
Everything is working fine, but I'm trying to get the coordinates of all the possible solutions. The problem is that if I put it inside col == n
it just prints the last one. Any ideas of how to solve this?
static void placement(int col, int queens[], int n){
//int solution =0;
for (int row = 1; row <= n; row++) {
queens[col] = row;
if((check_Queen(row,col,queens)) == true)
{
if((check_KnightMove(row,col,queens)) == true)
{
if(col == n)
{
System.out.println("("+row + "," + col);
System.out.println("solution=" + solution);
solution++;
}
else
{
placement(col+1,queens,n);
}
}
}
}
queens[col] = 0;
}
public static void main(String[] args) {
int solution =0;
Scanner scanner=new Scanner(System.in);
System.out.print("Please enter N");
int n = scanner.nextInt();// TODO Auto-generated method stub
int queens[] = new int[n+1];
placement(1,queens,n);
System.out.println("nQueens: solution=" + solution);
}
static boolean check_Queen(int row, int col, int queens[])
{
//boolean flag = false;
for(int i =1; i<col; i++)
{
if (queens[col-i] == row ||
queens[col-i] == row-i ||
queens[col-i] == row+i) {
//flag = false;
return false;
}
}
return true;
}
static boolean check_KnightMove(int row, int col, int queens[])
{
if(col>=2&&(queens[col-2] == (row -1) || queens[col-2] == (row+1) || queens[col-1] == (row-2) || queens[col-1] == (row+2)))
{
return false;
}
return true;
}
}
回答1:
It is hard to tell what is wrong in your solution without knowing how check_Queen
and check_KnightMove
are defined. Here is how I would solve the task:
public class Queens
{
static void printSolution (int [] queens)
{
int l = queens.length;
for (int i = 0; i < l; i++)
{
for (int j = 0; j < l; j++)
{
System.out.print (queens [i] == j ? 'Q' : '.');
System.out.print (' ');
}
System.out.println ();
}
System.out.println ();
}
static int placement (int [] queens, int c)
{
if (c == queens.length)
{
printSolution (queens);
return 1;
}
else
{
int solutionCount = 0;
int l = queens.length;
for (int r = 0; r < l; r++)
{
boolean flag = false;
for (int i = 0; i < c; i++)
{
int xd = c - i;
int yd = Math.abs (r - queens [i]);
if (yd == 0 || xd == yd)
{
flag = true;
break;
}
// Knight move support
if ((xd == 1 && yd == 2) || (xd == 2 && yd == 1))
{
flag = true;
break;
}
}
if (!flag)
{
queens [c] = r;
solutionCount += placement (queens, c + 1);
}
}
return solutionCount;
}
}
public static void main (String [] args)
{
System.out.println (
"Total solutions found: " + placement (new int [11], 0));
}
}
In your solution, method check_KnightMove
is incorrect. When col == 2
it does not allow Queen to be placed at row 1, because it believes that there is always a Queen at (col: 0, row: 0)
, i.e. outside the board. Here is corrected version:
static boolean check_KnightMove (int row, int col, int queens[])
{
if (col >= 3
&& (queens [col - 2] == (row - 1) || queens [col - 2] == (row + 1)))
{
return false;
}
if (col >= 2
&& (queens [col - 1] == (row - 2) || queens [col - 1] == (row + 2)))
{
return false;
}
return true;
}
来源:https://stackoverflow.com/questions/14888055/n-n-queen-algorithm-getting-the-coordinates