Find largest sub-array formed by consecutive integers

Given an array of integers, find largest sub-array formed by consecutive integers. The sub-array should contain all distinct values.


For example,

Input:  { 2, 0, 2, 1, 4, 3, 1, 0 }
Output: The largest sub-array is { 0, 2, 1, 4, 3 }


The idea is to consider every sub-array and keep track of largest subarray found so far which is formed by consecutive integers. In order for an sub-array to contain consecutive integers,

  • The difference between maximum and minimum element in it should be exactly equal to length of the subarray minus one.
  • All elements in the array should be distinct (we can check this by inserting the elements in set or using a visited array).


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The largest sub-array is [1, 5]

The time complexity of above solution is O(n3) and auxiliary space used by the program is O(n).

Exercise: Extend the solution to consider duplicates in the sub-array.

Thanks for reading.

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I think a sliding-window approach can accomplish this in linear time.

Thank you for posting so many helpful practice problems!

Cliff Crosland
Cliff Crosland

Cool – you can get O(n^2) time here by building the set as you go along in the inner loop that iterates through j. If max – min == j – i, and if all of the values between i and j are distinct (which you can tell from the set size), then you know immediately that the subsequence consists of the consecutive integers in the range [min, max].

You can also break out of the inner loop early if you ever run into a duplicate.

Will think about Dimitriy’s O(n) hint, cool…

Renjith Varma
Renjith Varma

This is O(n3) solution