Write a Python function to find the longest common prefix among multiple strings.
RoseHrs
Posted by RoseHrs
Last Updated: August 25, 2024
Python Strings
Finding the Longest Common Prefix in Python
When working with a list of strings, you may want to identify the longest common prefix shared among them. The longest common prefix is the longest substring that appears at the start of all strings in the list. Below is a Python function that accomplishes this task.
Function Implementation
def longest_common_prefix(strs):
    if not strs:
        return ""
    
    # Initialize the prefix to be the entire first string
    prefix = strs[0]
    
    for string in strs[1:]:
        # Check the current string against the current prefix
        while string[:len(prefix)] != prefix and prefix:
            # Reduce the prefix by one character from the end
            prefix = prefix[:-1]
        
        # If there is no common prefix
        if not prefix:
            return ""
    
    return prefix
Explanation of the Function
1. Input Check: The function first checks if the input list strs is empty. If it is, it returns an empty string, as there would be no common prefix. 2. Initial Prefix: The prefix is initialized to the first string in the list. This serves as the baseline for comparison. 3. Iteration Through Strings: The function then iterates through each subsequent string in the list. For each string, it checks if the current prefix matches the beginning of the string. 4. Adjusting the Prefix: If the prefix does not match the current string, the function trims the prefix by removing the last character. This is repeated until a match is found or the prefix becomes empty. 5. Final Return: Once all strings have been processed, the function returns the longest common prefix. If no common prefix exists, it returns an empty string.
Example Usage
Here’s how you can use the function: 
strings = ["flower", "flow", "flight"]
result = longest_common_prefix(strings)
print(result)  # Output: "fl"
Conclusion
The longest_common_prefix function is an efficient way to determine the common starting substring among a list of strings. This functionality is particularly useful in various applications, such as autocomplete features or clustering algorithms, where prefixes play a significant role in categorization.
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