14. Longest Common Prefix - leetcode - python - easy

 

Write a function to find the longest common prefix string amongst an array of strings.

If there is no common prefix, return an empty string "".

 

Example 1:

Input: strs = ["flower","flow","flight"]
Output: "fl"

Example 2:

Input: strs = ["dog","racecar","car"]
Output: ""
Explanation: There is no common prefix among the input strings.

 

Constraints:

• 1 <= strs.length <= 200
• 0 <= strs[i].length <= 200
• strs[i] consists of only lowercase English letters if it is non-empty.

class Solution:

    def longestCommonPrefix(self, strs: list[str]) -> str:

        if not strs:

            return ""

        pref = strs[0]

        for s in strs[1:]:

            while not s.startswith(pref):

                pref = pref[:-1]

                if not pref:

                    return ""

        return pref

Explanation (Simple Version)

Take the first string as the initial prefix.

Loop through the other strings:

If the current string doesn’t start with the prefix → remove the last character of the prefix. Repeat until all strings match → return the prefix.

If no common prefix → return "".