namespace WindowsFormApp1
{
    public partial class Form1 : Form
    {
        const int N = 4;//按鈕的行列數
        Button[,] buttons = new Button[N, N];//按鈕的陣列
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            
 
//生成按鈕
            GenerateAllButtons();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            //打亂順序
            Shuffle();
        }
        #region 打亂順序
        void Shuffle()
        {
            Random rnd = new Random();
            for (int i = 0; i < 100
 
; i++)//迴圈
            {
                int a = rnd.Next(N);
                //[0,N-1]行號，列號；生成 2行 2列
                int b = rnd.Next(N);
                int c = rnd.Next(N);
                int d = rnd.Next(N);
                Swap(buttons[a, b], buttons[c, d]);  //進行交換
            }
        }
        //交換兩個按鈕
 

        void Swap(Button btna, Button btnb)
        {
            string t = btna.Text;
            btna.Text = btnb.Text;
            btnb.Text = t;
            bool v = btna.Visible;
            btna.Visible = btnb.Visible;
            btnb.Visible = v;
        }

        #endregion
        #region 
        //生成按鈕
        void GenerateAllButtons()
        {
            int x0 = 100, y0 = 10, w = 45, d = 50;
            for (int r = 0; r < N; r++)    // 使用 r<arr.GetLength(0) c<arr.GetLength(1)
                for (int c = 0; c < N; c++)
                {
                    int num = r * N + c;
                    Button btn = new Button();
                    btn.Text = (num + 1).ToString();
                    btn.Top = y0 + r * d;
                    btn.Left = x0 + c * d;
                    btn.Width = w;
                    btn.Height = w;
                    btn.Visible = true;
                    btn.Tag = r * N + c;
                    btn.Click += Btn_Click;   //註冊click事件
                    buttons[r, c] = btn;           //放到陣列中
                    this.Controls.Add(btn);        //放到介面上
                }
            buttons[N - 1, N - 1].Visible = false;//最後一個按鈕隱藏
        }

        #endregion

        #region 移動按鈕
        void Btn_Click(object sender, EventArgs e)
        {
            //throw new NotImplementedException();
            Button btn = sender as Button; //把sender實參作為button，e存放sender的全部資訊
            Button blank = FindHiddenButton();//空白按鈕
            if (IsNeighbor(btn, blank))//判斷是否與空白塊相鄰，如果是，則交換
            {
                Swap(btn, blank);
                blank.Focus();
            }
            if (ResultIsOk())
            {
                MessageBox.Show("ok");
            }
        }
        
        //查詢要隱藏的按鈕
        Button FindHiddenButton()
        {
            for (int r = 0; r < N; r++)      
                for (int c = 0; c < N; c++)
                {
                    if (!buttons[r, c].Visible)
                        return buttons[r, c];
                }
            return null;
        }
        #endregion

        //判斷是否相鄰
        bool IsNeighbor(Button btnA, Button btnB)
        {
            int a = (int)btnA.Tag;
            int b = (int)btnB.Tag;
            int r1 = a / N, c1 = a % N;
            int r2 = b / N, c2 = b % N;
            if (r1 == r2 && (c1 == c2 - 1 || c1 == c2 + 1)//左右相鄰，行號相等，列號差一
                || c1 == c2 && (r1 == r2 - 1 || r1 == r2 + 1))//上下相鄰，列號相等，行號差一
                return true;
            return false;
        }
        //檢查是否完成
        bool ResultIsOk()
        {
            for (int r = 0; r < N; r++)
                for (int c = 0; c < N; c++)
                {
                    if (buttons[r, c].Text != (r * N + c + 1).ToString())
                        return false;
                }
            return true;
        }
    }
}