题目:
题解:
func wiggleSort(nums []int) {
n := len(nums)
x := (n + 1) / 2
target := quickSelect(nums, x-1)
transAddress := func(i int) int { return (2*n - 2*i - 1) % (n | 1) }
for k, i, j := 0, 0, n-1; k <= j; k++ {
tk := transAddress(k)
if nums[tk] > target {
for j > k && nums[transAddress(j)] > target {
j--
}
tj := transAddress(j)
nums[tk], nums[tj] = nums[tj], nums[tk]
j--
}
if nums[tk] < target {
ti := transAddress(i)
nums[tk], nums[ti] = nums[ti], nums[tk]
i++
}
}
}
func quickSelect(a []int, k int) int {
rand.Seed(time.Now().UnixNano())
rand.Shuffle(len(a), func(i, j int) { a[i], a[j] = a[j], a[i] })
for l, r := 0, len(a)-1; l < r; {
pivot := a[l]
i, j := l, r+1
for {
for i++; i < r && a[i] < pivot; i++ {
}
for j--; j > l && a[j] > pivot; j-- {
}
if i >= j {
break
}
a[i], a[j] = a[j], a[i]
}
a[l], a[j] = a[j], pivot
if j == k {
break
} else if j < k {
l = j + 1
} else {
r = j - 1
}
}
return a[k]
}