BM98 螺旋矩阵

https://www.nowcoder.com/practice/7edf70f2d29c4b599693dc3aaeea1d31

这道题目的话属于一道模拟题，只需要找出输出的规则和边界终止条件即可。

func spiralOrder(matrix [][]int) []int {
    if len(matrix) == 0 {
        return []int{}
    }

    var nums []int
    top, bottom, right, left := 0, len(matrix)-1, len(matrix[0])-1, 0
    for top < bottom && left < right {
        // 上层
        for i := left; i < right; i++ {
            nums = append(nums, matrix[top][i])
        }
        // 右层
        for i := top; i < bottom; i++ {
            nums = append(nums, matrix[i][right])
        }
        // 下层
        for i := right; i > left; i-- {
            nums = append(nums, matrix[bottom][i])
        }
        // 左层
        for i := bottom; i > top; i-- {
            nums = append(nums, matrix[i][left])
        }

        right--
        left++
        top++
        bottom--
    }

    if bottom == top {
        for i := left; i <= right; i++ {
            nums = append(nums, matrix[top][i])
        }
    } else if left == right {
        for i := top; i <= bottom; i++ {
            nums = append(nums, matrix[i][left])
        }
    }

    return nums
}