遍历螺旋矩阵算法

同事说最近螺旋矩阵挺火，笔者简单试了试，实现以下算法。

int[][] array = {
        {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}
};

image.png

如上图，需要遍历这种特殊的二维数组。我们可以看出遍历的顺序是从左到右，再从上到下，再从右到左，再从下到上，然后一直循环。我们这里还有4个标记，一个是从上到下当前行的标记，从下到上行的标记，从左到右从右到左的二个列的标记，当循环遍历的时候，这4个标记逐渐向中间靠拢，直到重合循环结束。
以上算法不只是适用于方阵，也适用于行数和列数不一样的任何矩阵。Java实现的算法如下：

int[][] array = {
        {1, 2, 3, 4, 5, 6},
        {18, 19, 20, 21, 22, 7},
        {17, 28, 29, 30, 23, 8},
        {16, 27, 26, 25, 24, 9},
        {15, 14, 13, 12, 11, 10}
};
int row = 5;
int column = 6;
//四个标记
int rowFromTop = 0;
int rowFromBottom = row - 1;
int columnFromRight = column - 1;
int columnFromLeft = 0;
int index = 0;
//遍历的方向，初始是向右方向
String direction = "右";
for (int i = 0; i < row * column; i++) {
    if (direction.equals("右")) {
        System.out.println(array[rowFromTop][index]);
        index++;
        if (index > columnFromRight) {
            direction = "下";
            rowFromTop++;
            index = rowFromTop;
        }
    } else if (direction.equals("下")) {
        System.out.println(array[index][columnFromRight]);
        index++;
        if (index > rowFromBottom) {
            direction = "左";
            columnFromRight--;
            index = columnFromRight;
        }
    } else if (direction.equals("左")) {
        System.out.println(array[rowFromBottom][index]);
        index--;
        if (index < columnFromLeft) {
            direction = "上";
            rowFromBottom--;
            index = rowFromBottom;
        }
    } else if (direction.equals("上")) {
        System.out.println(array[index][columnFromLeft]);
        index--;
        if (index < rowFromTop) {
            direction = "右";
            columnFromLeft++;
            index = columnFromLeft;
        }
    }
}