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Find All Numbers Disappeared in an Array

Medium

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Given an array of integers where 1 ≤ a[i] ≤ n, find all numbers in [1,n] that do not appear in the array.

Sample Input:

[4,3,2,7,8,2,3,1]

Sample Output:

[5,6]

Hints

Hint 1

Use array indices as markers

Hint 2

For each number, mark the position at index num-1 as negative

Hint 3

Positive indices indicate missing numbers

Code Editor

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