Longest Common Prefix

Lecture 72 :- Longest Common Prefix

The longest common prefix is a common problem in computer science and string processing. Given an array of strings, the task is to find the longest common prefix (LCP) among them. The LCP is the longest sequence of characters that is common to all the strings in the array, starting from the beginning of each string.

Here's an algorithm to find the longest common prefix:

1. Initialize the longest common prefix (LCP) variable to an empty string.
2. If the array of strings is empty, return an empty string as the LCP.
3. Take the first string in the array as the reference string.
4. Iterate through the characters of the reference string from the first character to the last.
5. For each character, check if it exists in the same position in all other strings.
6. If all characters match in the current position, append the character to the LCP.
7. If any character does not match in the current position, return the LCP found so far.
8. Continue this process until you have iterated through all characters in the reference string.
9. The resulting LCP will be the longest common prefix among all the strings in the array.

Here's a Python function to implement the algorithm:

pythonCopy code

def longest_common_prefix(strs):    if not strs:        return ""    # Take the first string as the reference string    reference_str = strs[0]    lcp = ""    for i in range(len(reference_str)):        char = reference_str[i]        # Check if the character exists in the same position in all other strings        for s in strs[1:]:            if i >= len(s) or s[i] != char:                return lcp        # Append the character to the LCP if it exists in all strings        lcp += char    return lcp # Example usage: strings = ["flower", "flow", "flight"] print(longest_common_prefix(strings))  # Output: "fl"

Keep in mind that the above algorithm has a time complexity of O(N*M), where N is the number of strings in the array, and M is the length of the longest string. It will go through all characters in the reference string and check each character in the other strings until it finds the longest common prefix or until it reaches the end of the reference string.