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

Last update on March 21 2025 12:42:16 (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:

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.

Python Code Editor:

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