Python Interview Question of the Day: Longest Substring Without Repeating Characters

You Should Know:

To solve the problem of finding the longest substring without repeating characters, you can use the sliding window technique. Below is a Python implementation:

def longest_substring_without_repeating_characters(s):
char_index_map = {}
left = 0
max_length = 0

for right, char in enumerate(s):
if char in char_index_map and char_index_map[char] >= left:
left = char_index_map[char] + 1
char_index_map[char] = right
max_length = max(max_length, right - left + 1)

return max_length

<h1>Example usage:</h1>

input_string = "abcabcbb"
print("Length of the longest substring without repeating characters:", longest_substring_without_repeating_characters(input_string))

Explanation:

– `char_index_map` keeps track of the last index of each character.
– `left` is the starting index of the current window.
– `right` is the ending index of the current window.
– If a character repeats and is within the current window, move the `left` pointer to the right of the previous occurrence.
– Update the maximum length of the substring found so far.

Practice Commands:

1. Linux Command to Count Unique Characters in a File:

   cat filename.txt | fold -w1 | sort | uniq | wc -l
   

2. Windows PowerShell Command to Find Unique Characters:

(Get-Content filename.txt).ToCharArray() | Sort-Object | Get-Unique | Measure-Object | Select-Object -ExpandProperty Count

1. Linux Command to Find Longest Line in a File:

   awk '{ if (length($0) > max) max = length($0) } END { print max }' filename.txt
   

2. Windows Command to Find Longest Line in a File:

   Get-Content filename.txt | Measure-Object -Property Length -Maximum | Select-Object -ExpandProperty Maximum
   

What Undercode Say:

Mastering string manipulation and algorithms like the sliding window technique is crucial for coding interviews and real-world problem-solving. Practice similar problems to strengthen your skills. For further reading, check out these resources:

• GeeksforGeeks: Sliding Window Technique
• LeetCode: Longest Substring Without Repeating Characters

Keep practicing and refining your approach to tackle more complex challenges in the future.

References:

Reported By: Tanu Nanda – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅