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Leetcode Problem 442. Find All Duplicates in an Array

442. Find All Duplicates in an Array

Leetcode Solutions

Approach: Mark Visited Elements in the Input Array itself

  1. Initialize an empty list to store the duplicates.
  2. Iterate over each element x in the array.
  3. Calculate the index idx as abs(x) - 1.
  4. If the element at nums[idx] is positive, negate it to mark that the number x has been seen.
  5. If the element at nums[idx] is already negative, it means x has been seen before, so add abs(x) to the list of duplicates.
  6. Return the list of duplicates.
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Approach: Store Seen Elements in a Set / Map

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