package cap3

func Ex38(k int, nums []int) {
    gcd := func(m, n int) int {
        a, b := m, n
        if m < n {
            a, b = n, m
        }

        r := a % b
        for r != 0 {
            a = b
            b = r
            r = a % b
        }

        return b
    }

    numsLen := len(nums)
    first, gcdNumb := 0, gcd(numsLen, k)
    for i := 0; i < gcdNumb; i++ {
        first = nums[i]
        startIdx := i
        for j := 0; j < numsLen/gcdNumb; j++ {
            startIdx = (startIdx + k) % numsLen
            // 交换
            tmp := nums[startIdx]
            nums[startIdx] = first
            first = tmp
        }
    }
}