N皇后问题可视化实现（java）

package queens;
import java.awt.Color;
import java.awt.GridLayout;
import java.awt.Image;
import java.io.IOException;
import java.util.Scanner;

import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;

class scan {
public static Scanner instance = new Scanner(System.in);
}

class queen{
ImageIcon image = new ImageIcon("queen.png");//JLabel的皇后图标
public int num = 0;	//皇后数量
public int sum = 0;	//解的计数器
public int set = 0;	//落子次数
public int[] a;

JFrame frame = new JFrame("棋盘");
JLabel lab[][] = null;
Scanner s;

//构造函数，初始化问题的规模
queen(){
System.out.print("请输入皇后数量：");
s = scan.instance;
num = s.nextInt();
sum = 0;
a = new int[num];
}

queen(int n){
num = n;
sum = 0;
a = new int[num];
}

//不带可视化计时间的n皇后回溯
public void backtrack(int t){
if (t >= num){
sum++;				//解数++
}
else{
for(int j = 0;j < num ;j++){
a[t] = j;		//假设第t行第j列放棋子
if (place(t)) {	//是否落子
set++;		//落子步数++
backtrack(t+1);	//落子，进入下一深度			//递归调用
}
}
}
}

//带可视化不计时间的n皇后
public void bbacktrack(int t){
if (t >= num){			//判断是否超出棋盘大小
sum++;
for(int i = 0;i < num; i++){
System.out.print(a[i] + " ");
}
System.out.println();
try {
Thread.sleep(1000);			//休眠1s
} catch (InterruptedException e) {
e.printStackTrace();
}
}
else{
for(int j = 0;j < num ;j++){

a[t] = j;		//先将第t行放入j

if (place(t)) {	//判断是否落子
try {
Thread.sleep(500);	//休眠0.1s
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
lab[t][a[t]].setIcon(image);	//落子
bbacktrack(t+1);					//递归调用
}
lab[t][a[t]].setIcon(null);
}
}
}

public boolean place(int t){	//判断是否落子，与减枝
for(int i = 0; i < t;i++){
//判断是否在同一列
if(a[i] == a[t]) return false;
//判断是否在同一斜线
if((t-i)== Math.abs(a[t]-a[i])) return false;
}
return true;
}

public void chessboard(){		//棋盘绘制
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(500, 500);
frame.setResizable(false);
frame.setLocation(200,0);
Image img = image.getImage();
img = img.getScaledInstance(100, 100, Image.SCALE_DEFAULT);
image.setImage(img);
frame.setVisible(true);
frame.setLayout(new GridLayout(num,num));
frame.setSize(num*100, num*100);
frame.setResizable(true);
lab = new JLabel[num][num];
for(int i = 0;i <num;i++){
for(int j = 0;j < num;j++){
lab[i][j] = new JLabel();
lab[i][j].setOpaque(true);//设置为透明，才能显示背景色
if((i+j)%2==0){
lab[i][j].setBackground(Color.gray);
}
else{
lab[i][j].setBackground(Color.white);
}
frame.add(lab[i][j]);
}
}
}

};

public class run {
public static void run_q(int x){
Scanner s = scan.instance;
if (x == 0){
System.out.println("请输入你想要测试的规模：" );
int max = scan.instance.nextInt();
for (int i=1 ;i <= max ;i++){
queen q = new queen(i);
long start = System.nanoTime();
q.backtrack(0);
long end = System.nanoTime();
System.out.print( i + "皇后有" + q.sum + "种解 ，落子步数:" + q.set);
System.out.println("用时:" + ((end-start)/1000000.000) + "ms");
}

}
else if ( x == 1){
queen q = new queen();
q.chessboard();
q.bbacktrack(0);
}
else if ( x == 2){
System.out.print("请输入你想要测试的规模：" );
int n = s.nextInt();
boolean flag = true;
System.out.println("请依此输入你想要的测试数据：");
queen q = new queen(n);
for(int i=0 ;i<n;i++)
q.a[i] = -1;
for(int i=0 ;i<n;i++){
int index = s.nextInt()-1;
if(q.a[index] == -1){	//判断是否之前有输入这一行的数据，有就直接失败
q.a[index] = s.nextInt()-1;
if (!q.place(i)) {flag = false;break;}//判断是否冲突
}
else {flag = false; break;}
}
if(!flag){
System.out.println("失败");
}
else{
System.out.println("成功");
}
}

}

public static void run_t() throws InterruptedException{

boolean flag = true;
while(flag){
Scanner s = scan.instance;
System.out.print("请输入数字，0测试计算时间，1代表可视化，2代表数据测试：");
int x = s.nextInt();
run_q(x);
System.out.print("是否继续（y/n）：");
String c = s.next();
if( c.equals("n")) flag = false;

}
}
public static void main(String[] args) throws IOException, InterruptedException {
run_t();

}
}