算法系列——八皇后问题

public class Queen {
    private final int size;
    private int[] location;
    private int[] columnOccupied;
    private int[] lineOccupied;            //对角线
    private int[] reverseLineOccupied;     //反对角线
    private static int solveCount;
    private static final int locationOccupied = 1;
    private static final int unLocationOccupied = 0;
    
    public Queen(int size){
        this.size = size;
        location = new int[size];
        columnOccupied = new int[size];
        lineOccupied= new int[2*size];
        reverseLineOccupied = new int[2*size];
    }
    
    public void printLocation(){
        System.out.println("第"+solveCount+"方法");
        for(int i=0;i<size;i++){
            System.out.println("行"+i+"列"+location[i]);
        }
    }
    
    private boolean isOccupied(int i,int j){
        return(columnOccupied[j]==locationOccupied)||                   //列被占据
            (lineOccupied[i-j-1+size]==locationOccupied)||              //斜线被占据
                (reverseLineOccupied[i+j]==locationOccupied);          //反斜线被占
    }
    
    public void setLocation(int i,int j,int flag){
        columnOccupied[j] = flag;
        lineOccupied[i-j-1+size] = flag;
        reverseLineOccupied[i+j] = flag;
    }
    public void place(int i){
        for(int j=0;j<size;j++){
            if(!isOccupied(i,j)){
                location[i] = j;
                setLocation(i,j,locationOccupied);
             
                if(i<size-1){
                    place(i+1);
                 
                }else{
                    solveCount++;
                    printLocation();
                
                }
                setLocation(i,j,unLocationOccupied);
            }
        }
    }
    public  void start(int i){
        place(i);
    }

    public static void main(String[] args){
          new Queen(8).start(0);
         
        
    }
     
}