Write a program to find missing numbers in a sorted list using Python

Problem : Given a sorted list of integers but some are missing, write a Python program to find all the missing integers.

Example :

Input : [1, 2, 4, 6, 7, 9, 10] Output : [3, 5, 8] Input : [5, 6, 10, 11, 13] Output : [7, 8, 9, 12]

In this article, TipsMake.com will learn with you how to write a program to find missing numbers in a sorted list using Python.

Method 1: Use List Comprehension

You can work around this with Python's built-in List Comprehension. Here is the sample code for your reference:

# Python3 program to Find missing # integers in list def find_missing(lst): max = lst[0] for i in lst : if i > max : max= i min = lst [0] for i in lst : if i < min: min = i missing = max+1 list1=[] for _ in lst : max = max -1 if max not in lst : list1.append(max) return list1 # Driver code lst = [1,5,4,6,8, 2,3, 7, 9, 10] print(find_missing(lst))

The returned result is:

[3, 5, 8]

Method 2: Use List Comprehension with zip()

Still similar to method 1, but you use zip() to shorten the code. Here is sample code:

# Python3 program to Find missing # integers in list def find_missing(lst): return [i for x, y in zip(lst, lst[1:]) for i in range(x + 1, y) if y - x > 1] # Driver code lst = [1, 2, 4, 6, 7, 9, 10] print(find_missing(lst))

The returned result is:

[3, 5, 8]

Method 3: Using set

Using Python's set is an efficient and simple way to find missing numbers in a list. We will convert the list to a set and simply output the difference between this set and the set of integers min to max.

Here is the sample code for your reference:

# Python3 program to Find missing # integers in list def find_missing(lst): return sorted(set(range(lst[0], lst[-1])) - set(lst)) # Driver code lst = [1, 2, 4, 6, 7, 9, 10, 12, 13, 15] print(find_missing(lst))

The returned result is:

[3, 5, 8, 11, 14]

Method 4: Use difference()

This is a similar approach to #3. However, with a slight difference, instead of using the "-" operator to find the difference between two sets, we can use the difference( ) of Python.

Here is sample code:

# Python3 program to Find missing # integers in list def find_missing(lst): start = lst[0] end = lst[-1] return sorted(set(range(start, end + 1)).difference(lst)) # Driver code lst = [1, 2, 4, 6, 7, 9, 10] print(find_missing(lst))

The returned result is:

[3, 5, 8]

Conclude

Finding the missing number in the sorted list is a frequently asked question by employers to check the qualifications of candidates. TipsMake.com hopes that this article will help you.

Jessica Tanner

Update 27 June 2023