package main

import "fmt"

func main() {
    nums := []int{4, 3, 2, 7, 8, 2, 3, 1}
    ret := findDisappearedNumbers(nums)
    fmt.Println(ret)
}

func findDisappearedNumbers(nums []int) []int {
    ans := make([]int, 0)
    if len(nums) == 0 {
        return ans
    }
    N := len(nums)
    for i := 0; i < N; i++ {
        // 从i位置出发，去玩下标循环怼
        walk(nums, i)
    }
    for i := 0; i < N; i++ {
        if nums[i] != i+1 {
            ans = append(ans, i+1)
        }
    }
    return ans
}

func walk(nums []int, i int) {
    for nums[i] != i+1 { // 不断从i发货
        nexti := nums[i] - 1
        if nums[nexti] == nexti+1 {
            break
        }
        nums[i], nums[nexti] = nums[nexti], nums[i]
    }
}