const int ROW__ = 10;
const int COL__ = 10;
int mat[ROW__][COL__];

struct Position
{
	int nRow;
	int nCol;
};

int main(int argc, char* argv[])
{
	Position offset[4];
	//从左至右，行号不变，列号加一
	offset[0].nRow = 0;
	offset[0].nCol = 1;
	//从上至下，行号加一，列号不变
	offset[1].nRow = 1;
	offset[1].nCol = 0;
	//从右至左，行号不变，列号减一
	offset[2].nRow = 0;
	offset[2].nCol = -1;
	//从下至上，行号减一，列号不变
	offset[3].nRow = -1;
	offset[3].nCol = 0;

	Position curPos;
	curPos.nRow = 0;
	curPos.nCol = 0;
	mat[0][0] = 1;

	int nOffset = 0;

	Position tempPos;
	for (int i = 1; i < ROW__*COL__; i++)
	{
		// nOffset % 4 ------> 右->下->左->上 循环
		tempPos.nRow = curPos.nRow + offset[nOffset % 4].nRow;
		tempPos.nCol = curPos.nCol + offset[nOffset % 4].nCol;

		if (tempPos.nRow >= ROW__ || tempPos.nRow < 0
				|| tempPos.nCol >= COL__ || tempPos.nCol < 0 // 不超过边界
				|| mat[tempPos.nRow][tempPos.nCol] > 0) // 已经有值
		{
			i--;
			nOffset++;
			continue;
		}	

		curPos = tempPos;
		mat[curPos.nRow][curPos.nCol] = i + 1;
	}
	
	return 0;
}