lavos/cap3/ex21.go

package cap3

// Ex21 螺旋阵
func Ex21(n int) [][]int {
	matrix := _makeMatrix(n)

	// 逐层往里填充
	num := 1
	for layer := 0; layer < n/2; layer++ {
		// 方阵左边
		for i := layer; i < n-layer; i++ {
			matrix[i][layer] = num
			num++
		}

		// 方阵下边
		for i := layer + 1; i < n-layer; i++ {
			matrix[n-layer-1][i] = num
			num++
		}

		// 方阵右边
		for i := n - layer - 2; i >= layer; i-- {
			matrix[i][n-layer-1] = num
			num++
		}

		// 方阵上边
		for i := n - layer - 2; i > layer; i-- {
			matrix[layer][i] = num
			num++
		}
	}

	// 奇数阶中间位置需要手动设置
	if n%2 != 0 {
		matrix[n/2][n/2] = n * n
	}

	return matrix
}

func Ex21type2(n int) [][]int {
	matrix := _makeMatrix(n + 10)

	row, col, t := 0, 0, 1

	for i := 0; i < n*n; {
		for j := 0; j < 2*n; j++ {
			i++
			matrix[row][col] = i

			switch (j + 1) / (n + 1) {
			case 0:
				row += t
			case 1:
				col += t
			}
		}

		n--
		t = -t
	}

	return matrix
}