cc150_9_9.java

import java.util.ArrayList;

public class Q9_9 {
	
	
//	static int cnt = 0;
	static int GRID_SIZE = 8;
	public static void placeQueens(int row, Integer[] columns, ArrayList<Integer[]> results){
		
		if (row == GRID_SIZE){
			for(int i = 0; i < columns.length;i++){
				System.out.print(columns[i]);
				}
//			cnt ++;
			System.out.println();
//			System.out.println(cnt);
			
			results.add(columns.clone());
		}else
		{
			for(int col = 0; col < GRID_SIZE; col ++){
				
				if(checkValid(columns,row,col)){
					columns[row] = col;
					
					placeQueens(row + 1,columns,results);
				}
				
			}
		}
	}
	
	
	private static boolean checkValid(Integer[] columns, int row1, int col1) {
		// TODO Auto-generated method stub
		for(int row2 = 0; row2 < row1; row2 ++){
			int col2 = columns[row2];
			
			if(col1 == col2) return false;
			
			int columnDistance = Math.abs(col2 - col1);
			int rowDistance = row1 - row2;
			if(columnDistance == rowDistance) return false;
			
			
		}
		
		
		return true;
	}


	public static void main(String[] args){
		Integer[] columns = new Integer[GRID_SIZE];
		
		ArrayList<Integer[]> rst = new ArrayList<Integer[]>();
		
		placeQueens(0, columns, rst);
		System.out.println(rst.size());
	}

}