Longest Common Prefix

Clarify the problem:

• The problem requires finding the longest common prefix among a given array of strings.
• We need to implement a function that takes an array of strings as input and returns the longest common prefix.

Analyze the problem:

• Input: An array of strings.
• Output: The longest common prefix as a string.
• Constraints:
  • The array can be empty.
  • The strings in the array may be empty or have different lengths.

Design an algorithm:

• We can find the longest common prefix by comparing characters at each position in all the strings.
• Start with the first character of the first string and compare it with the corresponding characters in other strings.
• If all characters match, append the character to the common prefix.
• Continue this process until a mismatch is found or we reach the end of any string.

Explain your approach:

• We will implement a function called longestCommonPrefix that takes an array of strings as input.
• If the array is empty, return an empty string.
• Initialize a variable prefix as an empty string to store the common prefix.
• Iterate through the characters of the first string.
• For each character, iterate through the remaining strings and compare the corresponding characters.
• If any character mismatches or we reach the end of any string, return the current prefix.
• If all characters match, append the character to the prefix.
• Return the final prefix.

Write clean and readable code:

python

def longestCommonPrefix(strs):
    if not strs:
        return ""

    prefix = ""
    for i, char in enumerate(strs[0]):
        for j in range(1, len(strs)):
            if i >= len(strs[j]) or char != strs[j][i]:
                return prefix
        prefix += char

    return prefix

Test your code:

python

# Test case 1
# Input: ["flower", "flow", "flight"]
# The longest common prefix is "fl".
assert longestCommonPrefix(["flower", "flow", "flight"]) == "fl"

# Test case 2
# Input: ["dog", "racecar", "car"]
# There is no common prefix, so the result is an empty string.
assert longestCommonPrefix(["dog", "racecar", "car"]) == ""

# Test case 3
# Input: ["a"]
# The longest common prefix is "a" since there is only one string.
assert longestCommonPrefix(["a"]) == "a"

Optimize if necessary:

• The provided solution has a time complexity of O(n * m), where n is the number of strings and m is the length of the longest string.
• The space complexity is O(1) since we use a constant amount of extra space.

Handle error cases:

• The given code assumes that the input strs is a valid array of strings. If the input is not a valid array or contains invalid values, it may result in unexpected behavior.

Discuss complexity analysis:

• The time complexity of the solution is O(n * m), where n is the number of strings and m is the length of the longest string. We iterate through the characters of the first string and compare them with the corresponding characters in other strings.
• The space complexity is O(1) since we use a constant amount of extra space to store the prefix.