Longest Common Prefix in Python

Suppose we have a set of strings in an array. We have to find the Longest Common Prefix amongst the string in the array. Here we will assume that all strings are lower case strings. And if there is no common prefix, then return “”.

So if the array of a string is like ["school", "schedule","Scotland"], then the Longest Common Prefix is “sc” as this is present in all of these string.

To solve this, we will take the first string as curr, now take each string from the array and read them character by character, and check the characters between curr, and the taken string one by one. If they are same go for next character, otherwise break the loop, and update the curr as the substring that has matched.

Let us see the implementation to get a better understanding

Example (Python)

 Live Demo

class Solution(object):
   def longestCommonPrefix(self, strs):
      """
      :type strs: List[str]
      :rtype: str
      """
      if len(strs) == 0:
         return ""
      current = strs[0]
      for i in range(1,len(strs)):
         temp = ""
         if len(current) == 0:
            break
         for j in range(len(strs[i])):
            if j<len(current) and current[j] == strs[i][j]:
               temp+=current[j]
            else:
               break
         current = temp
      return current
input_list = ["school","schedule","scotland"]
ob1 = Solution()
print(ob1.longestCommonPrefix(input_list))

Input

["school","schedule","scotland"]

Output

"sc"