Lesson overview · Free interview practice

Cyclic Sort

Sort an array with minimal extra space.

Topics in the full lesson
  • Concept and Use Cases
  • When to Use
  • Time and Space Complexity
  • Sorting an Array of Numbers from 1 to n
  • Finding Missing Numbers
  • Finding Duplicate Numbers

Practice Problems

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CodingEasy

Find All Numbers Disappeared in an Array

Question

Given an array nums of n integers where each integer is in the range [1, n], return an array of all the integers in [1, n] that do not appear in nums. Solve in O(n) time without using O(n) extra space (mark indices in-place).

Take a moment to think about this before revealing the answer

Explain your reasoning or try an implementation before comparing answers.

Practice on LeetCode
CodingMedium

Find All Duplicates in an Array

Question

Given an integer array nums of length n where each element is in the range [1, n] and each appears at most twice, return an array of all integers that appear exactly twice. Solve in O(n) time using O(1) extra space.

Take a moment to think about this before revealing the answer

Explain your reasoning or try an implementation before comparing answers.

Practice on LeetCode
CodingHard

First Missing Positive

Question

Given an unsorted integer array nums that may contain negatives, zeros, and duplicates, return the smallest positive integer that does not appear in it. Your algorithm must run in O(n) time and use O(1) auxiliary space.

Take a moment to think about this before revealing the answer

Explain your reasoning or try an implementation before comparing answers.

Practice on LeetCode

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