回旋矩阵

Mr.chenz — Sun, 25 Jul 2010 05:55:00 GMT

这是深圳某处的一个面试题，要求打印出如下格式：

int i=5;
1   2  3  4 5
16 17 18 19 6
15 24 25 20 7
14 23 22 21 8
13 12 11 10 9

int i=6
1   2  3  4  5  6
20 21 22 23 24  7
19 32 33 34 25  8
18 31 36 35 26  9
17 30 29 28 27 10
16 15 14 13 12 11

解决方案1：

public class SnakePrint {

    private int orient = 0, length = 0, x = 0, y = 0;
    // orients为顺时针90°旋转方向，前进步长为1
    private int[][] orients = { { 0, 1 }, { 1, 0 }, { 0, -1 }, { -1, 0 } };
    private int[][] arrays;

    public SnakePrint(int length) {
        this.length = length;
        arrays = new int[length][length];
    }

    // 根据当前方向返回下一个前进方向
    private int[] nextOrient(int[] curOrient) {
        int nextX = x + curOrient[0], nextY = y + curOrient[1];

        // 前进方向需要顺时针旋转90°了
        if (nextX < 0 || nextX >= length || nextY < 0 || nextY >= length
                || arrays[nextX][nextY] != 0) {
            orient = ++orient % 4;
            return orients[orient];
        }

        return curOrient; // 不需要掉头，返回原前进方向
    }

    public void print() {
        int[] curOrient = orients[orient]; // 初始前进方向
        for (int i = 1; i <= length * length; i++) { // 依次填充数组
            arrays[x][y] = i;
            curOrient = nextOrient(curOrient);
            x += curOrient[0];
            y += curOrient[1];
        }

        for (int i = 0; i < length; i++) {
            for (int j = 0; j < length; j++) {
                System.out.printf("%4d", arrays[i][j]); // 按固定4个字符宽度的格式输出
            }
            System.out.println();
        }
    }

    public static void main(String[] args) {
        SnakePrint snakePrint = new SnakePrint(6);
        snakePrint.print();
    }
}

解决方案2：

转化为二维数组初始化问题

class snakePrint {
    static int length = 7;
    static int value = 1;
    static int[][] snake = new int[length][length];
    static Direction lastDirection = Direction.Right;

    static enum Direction {
        Right, Down, Left, Up;
    }

    public static void initialArray() {
        int row = 0, line = 0;
        for (int c = 0; c < length * length; c++) {
            snake[row][line] = value;
            lastDirection = findDirection(row, line);
            switch (lastDirection) {
                case Right:
                    line++;
                    break;
                case Down:
                    row++;
                    break;
                case Left:
                    line--;
                    break;
                case Up:
                    row--;
                    break;
                default:
                    System.out.println("error");
            }
            value++;
        }
    }

    static Direction findDirection(int row, int line) {
        Direction direction = lastDirection;
        switch (direction) {
            case Right: {
                if ((line == length - 1) || (snake[row][line + 1] != 0))
                    direction = direction.Down;
                break;
            }
            case Down: {
                if ((row == length - 1) || (snake[row + 1][line] != 0))
                    direction = direction.Left;
                break;
            }
            case Left: {
                if ((line == 0) || (snake[row][line - 1] != 0))
                    direction = direction.Up;
                break;
            }
            case Up: {
                if (snake[row - 1][line] != 0)
                    direction = direction.Right;
                break;
            }
        }
        return direction;
    }

    public static void main(String[] args) {
        initialArray();

        // display..
        for (int i = 0; i < length; i++) {
            for (int j = 0; j < length; j++) {
                System.out.print(snake[i][j] + "  ");
            }
            System.out.println();
        }
    }
}

Mr.chenz 2010-07-25 13:55 发表评论

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回旋矩阵