Python: Find the longest common prefix string amongst a given array of strings

Last update on April 17 2025 13:01:19 (UTC/GMT +8 hours)

Longest Common Prefix

Write a Python program to find the longest common prefix string among a given array of strings. Return false if there is no common prefix.
For Example, longest common prefix of "abcdefgh" and "abcefgh" is "abc".

Sample Solution:

Python Code:

# Function to find the longest common prefix among a list of strings
def longest_Common_Prefix(str1):
    
    if not str1:  # Check if the list is empty
        return ""

    short_str = min(str1, key=len)  # Find the shortest string in the list

    for i, char in enumerate(short_str):  # Iterate through characters in the shortest string
        for other in str1:  # Iterate through other strings in the list
            if other[i] != char:  # Check if the corresponding characters don't match
                return short_str[:i]  # Return the common prefix found so far

    return short_str  # Return the entire shortest string if it is a common prefix

# Test cases
print(longest_Common_Prefix(["abcdefgh", "abcefgh"]))  # "abc"
print(longest_Common_Prefix(["w3r", "w3resource"]))  # "w3r"
print(longest_Common_Prefix(["Python", "PHP", "Perl"]))  # ""
print(longest_Common_Prefix(["Python", "PHP", "Java"]))  # ""

Sample Output:

abc
w3r
P

Explanation:

Here is a breakdown of the above Python code:

First define a function named "longest_Common_Prefix()" that takes a list of strings (str1) as input.
Check if the list is empty. If so, return an empty string.
Find the shortest string (short_str) in the list using the "min()" function with the key=len argument.
Iterate through the characters in the shortest string using 'enumerate'.
For each character, iterate through the other strings in the list and check if the corresponding characters match.
If a mismatch is found, return the common prefix found so far.
If no mismatch is found, return the entire shortest string as the common prefix.
Test the function with various input lists and print the results.

Visual Presentation:

Python: Find the longest common prefix string amongst a given array of strings

Flowchart:

For more Practice: Solve these Related Problems:

Write a Python program to find the longest common prefix among an array of strings using vertical scanning.
Write a Python program to compute the longest common prefix using horizontal scanning of string characters.
Write a Python program to determine the longest common prefix by sorting the list and comparing the first and last elements.
Write a Python program to implement a divide and conquer approach to find the longest common prefix in a list of strings.

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