# Find The Missing Integer

DevFeed: [Find The Missing Integer](<https://devfeed.tech/articles/find-the-missing-integer-34556.md>)

Original publisher: [Read original article](<https://tapoueh.org/blog/2017/05/find-the-missing-integer/>)

Author: Dimitri Fontaine PostgreSQL Major Contributor; Author

Published: 2017-05-30T17:56:54Z

Content type: article

Language: en

Sources: [Dimitri Fontaine](<https://devfeed.tech/sources/dimitri-fontaine.md>)

Topics: [Algorithm](<https://devfeed.tech/topics/algorithm.md>), [math](<https://devfeed.tech/topics/math.md>), [Common Lisp](<https://devfeed.tech/topics/common-lisp.md>), [Computer science](<https://devfeed.tech/topics/computer-science.md>), [Lisp](<https://devfeed.tech/topics/lisp.md>), [Python](<https://devfeed.tech/topics/python.md>), [Data structures](<https://devfeed.tech/topics/data-structures.md>)

Tags: [algorithm](<https://devfeed.tech/tags/algorithm.md>), [complexity](<https://devfeed.tech/tags/complexity.md>), [data-structure](<https://devfeed.tech/tags/data-structure.md>), [lisp](<https://devfeed.tech/tags/lisp.md>), [math](<https://devfeed.tech/tags/math.md>), [python](<https://devfeed.tech/tags/python.md>), [set](<https://devfeed.tech/tags/set.md>), [sorting](<https://devfeed.tech/tags/sorting.md>)

## AI overview

The article examines ways to find missing elements in a list. It contrasts sorting and the Gauss-sum method for one missing integer with set difference, which can handle multiple missing entries and arbitrary data types in Common Lisp and Python.

## Source excerpt

A recent interview question that I had to review was spelled like this: Find missing int element into array 1..100 Of course at first read I got it wrong, you have only one integer to look for into the array. So while the obvious idea was to apply classic sorting techniques and minimize array traversal to handle complexity (time and space), it turns out there's a much simpler way to do it if you remember your math lessons from younger. But is it that much simpler?