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();
}
}
}