Finding Duplicate Elements in an Array :: Phil! Gregory - The Diigo Meta page

• 13 Jun 12
  

  graju256
• 29 Sep 11
  

  Rodrigo Chappa

  algorithms puzzle graph

• 20 Sep 11
  

  Abhay Bothra

  algorithms puzzle

• 05 Feb 11
  

  Jeff Li

  algorithm

• 23 May 10
  

  Rajesh Singh

  repeated elements algorithms

• 15 May 09
  

  varkas

  and the only assurance you have is that the values are between 0 and n, exclusive. Is it still possible to find a duplicated value in O(n) time and O(1) space? Feel free to stop here and try to work things out yourself, if you want.

  algorithms

• 10 Oct 08
  

  Tristan Bailey

  programming algorithm

• 01 Jul 08
  

  kkotowicz

  find duplicate elements algorithm

• 03 Sep 07
  

  taylortree

  programming

  • Now, suppose that the array is of length n and only contains positive integers less than n. We can be sure (by the pigeonhole principle) that there is at least one duplicate.
  • So, how do we find the beginning of the cycle? The easiest approach is to use Floyd's cycle-finding algorithm. It works roughly like this: Start at the beginning of the sequence. Keep track of two values (call them a_i and a_j). At each step of the algorithm, move a_i one step along the sequence, but move a_j two steps. Stop when a_i = a_j.

Page Comments

• 
  taylortree on 2007-09-03
  Interesting way to find duplicates in an array.  Enjoyed the links on the pigeonhold principle and Floyd's cycle-finding algorithm.
  

Would you like to comment?

Join Diigo for a free account, or sign in if you are already a member.