Given a list of n integers where every value is in the range 1 to n (inclusive), some numbers appear more than once and others are missing. Return a list of all integers in the range 1 to n that do NOT appear in the input, in ascending order. Return an empty list for null or empty input.
Examples:
Input: nums = [4,3,2,7,8,2,3,1]
Output: [5,6]
Explanation: n = 8; 5 and 6 do not appear in the list
Input: nums = [1,1]
Output: [2]
Explanation: n = 2; 2 is missing because 1 appears twice
Input: nums = [1,2,3]
Output: []
Explanation: All values 1 to 3 are present, nothing is missing
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