Longest Common Prefix in DSA Python - Build from Scratch

Longest Common Prefix Finder

📖 Scenario: Imagine you are building a search suggestion feature for a website. When users type words, you want to find the longest common beginning part (prefix) of all their search queries to suggest completions.

🎯 Goal: Build a program that finds the longest common prefix string among a list of words.

📋 What You'll Learn

Create a list of words with exact values

Add a variable to hold the prefix result

Use a loop to compare characters of words

Print the longest common prefix found

💡 Why This Matters

🌍 Real World

Finding common prefixes helps in search suggestions, autocomplete features, and DNA sequence analysis.

💼 Career

Understanding string manipulation and loops is essential for software development, especially in text processing and user interface features.

1

Create the list of words

Create a list called words with these exact strings: "flower", "flow", "flight".

DSA Python

# Create the list of words
# Your code here

Hint

Use square brackets [] to create a list and separate words with commas.

2

Create a variable for the prefix

Create a variable called prefix and set it to the first word in the words list.

DSA Python

words = ["flower", "flow", "flight"]
# Create a variable called prefix and set it to words[0]
# Your code here

Hint

Use words[0] to get the first word from the list.

3

Find the longest common prefix

Use a for loop with variable word to iterate over words[1:]. Inside the loop, use a while loop to shorten prefix until it matches the start of word using word.startswith(prefix).

DSA Python

words = ["flower", "flow", "flight"]
prefix = words[0]
# Use a for loop to check each word in words[1:]
# Use a while loop to shorten prefix until it matches the start of word
# Your code here

Hint

Use word.startswith(prefix) to check if word begins with prefix. Shorten prefix by removing the last character until it matches.

4

Print the longest common prefix

Print the variable prefix to show the longest common prefix found.

DSA Python

words = ["flower", "flow", "flight"]
prefix = words[0]
for word in words[1:]:
    while not word.startswith(prefix):
        prefix = prefix[:-1]
# Print the prefix
# Your code here

Hint

Use print(prefix) to display the result.