Grokking the Coding Interview: Patterns for Coding Questions
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Solution: Find all Duplicate Numbers

Problem Statement

We are given an unsorted array containing n numbers taken from the range 1 to n. The array has some numbers appearing twice, find all these duplicate numbers using constant space.

Example 1:

Input: [3, 4, 4, 5, 5]
Output: [4, 5]

Example 2:

Input: [5, 4, 7, 2, 3, 5, 3]
Output: [3, 5]

Constraints:

  • nums.length == n
  • 1 <= n <= 10^5
  • 1 <= nums[i] <= n
  • Each element in nums appears once or twice.

Solution

This problem follows the Cyclic Sort pattern and shares similarities with Find the Duplicate Number

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