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func findDisappearedNumbers(nums []int) []int {
    for i := 0; i < len(nums); i++ {
        for nums[i] != i + 1 && nums[i] != nums[nums[i]-1] {
            nums[i], nums[nums[i]-1] = nums[nums[i]-1], nums[i]
        }
    }
    res := make([]int, 0)
    for i := 0; i < len(nums); i++ {
        if nums[i] != i + 1 {
            res = append(res, i+1)
        }
    }
    return res
}