package cap3

// Work3 从外到里填充矩阵
func Work3(n int) [][]int {
    matrix := make([][]int, n)
    for i := range matrix {
        matrix[i] = make([]int, n)
    }

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

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

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

        // 方阵左边
        for i := n - layer - 2; i > layer; i-- {
            matrix[i][layer] = 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
}