public class SnakeMatrix {
  /**
   * 定义矩阵的阶数
   */
  private int n;
  //填充矩阵的值
  private int k = 1;
  private int[][] data;
  /**
   * 定义矩阵移动的方向
   */
  public enum Direction {
    left, right, up, down,
  }
  SnakeMatrix(int n) {
    this.n = n;
    data = new int[n][n];
  }
  public void clockwisePrintMatrix() {
    //定义行数
    int rowLen = data.length;
    //定义列数
    int columnLen = data.length;
    //移动方向
    Direction direction = Direction.right;
    //定义上边界
    int upBound = 0;
    //定义下边界
    int downBound = rowLen - 1;
    //定义左边界
    int leftBound = 0;
    //定义右边界
    int rightBound = columnLen - 1;
    //矩阵当前行数
    int row = 0;
    //矩阵当前列数
    int column = 0;
    while (true) {
      data[row][column] = k++;
      if (upBound == downBound && leftBound == rightBound) {
        // System.out.println(" upBound :"+upBound +" downBound :"+downBound+" leftBound :"+leftBound +" rightBound :"+rightBound);
        break;
      }
      switch (direction) {
        case right:
          if (column < rightBound) {
            ++column;
          } else {
            ++row;
            direction = Direction.down;
            ++upBound;
          }
          break;
        case down:
          if (row < downBound) {
            ++row;
          } else {
            --column;
            direction = Direction.left;
            --rightBound;
          }
          break;
        case up:
          if (row > upBound) {
            --row;
          } else {
            ++column;
            direction = Direction.right;
            ++leftBound;
          }
          break;
        case left:
          if (column > leftBound) {
            --column;
          } else {
            --row;
            direction = Direction.up;
            --downBound;
          }
          break;
        default:
          break;
      }
    }
    for (int i = 0; i < n; i++) {
      for (int j = 0; j < n; j++) {
        System.out.printf("%2d%s", data[i][j], " ");
      }
      System.out.println();
    }
  }
  public void anticlockwisePrintMatrix() {
    int rowLen = data.length;
    int columnLen = data.length;
    int leftBound = 0;
    int rightBound = columnLen - 1;
    int upBound = 0;
    int downBound = rowLen - 1;
    int row = 0;
    int column = 0;
    Direction direction = Direction.down;
    while (true) {
      data[row][column] = k++;
      if (rightBound == leftBound && upBound == downBound) {
        break;
      }
      switch (direction) {
        case down:
          if (row < downBound) {
            row++;
          } else {
            column++;
            direction = Direction.right;
            leftBound++;
          }
          break;
        case right:
          if (column < rightBound) {
            column++;
          } else {
            row--;
            direction = Direction.up;
            downBound--;
          }
          break;
        case up:
          if (row > upBound) {
            row--;
          } else {
            direction = Direction.left;
            column--;
            rightBound--;
          }
          break;
        case left:
          if (column > leftBound) {
            column--;
          } else {
            direction = Direction.down;
            row++;
            upBound++;
          }
          break;
        default:
          break;
      }
    }
    for (int i = 0; i < n; i++) {
      for (int j = 0; j < n; j++) {
        System.out.printf("%2d%s", data[i][j], " ");
      }
      System.out.println();
    }
  }
}

public class MainActivity extends AppCompatActivity {
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    int number = 5;
    SnakeMatrix snakeMatrix = new SnakeMatrix(number);
    snakeMatrix.anticlockwisePrintMatrix();
    //snakeMatrix.clockwisePrintMatrix();
  }
}