leetcode 13.最长公共前缀

编写一个函数来查找字符串数组中的最长公共前缀。

如果不存在公共前缀，返回空字符串 ""。

class Solution:
    def longestCommonPrefix(self, strs):
        """
        :type strs: List[str]
        :rtype: str
        """
        if len(strs) == 0:
            return ""
        if len(strs) == 1:
            return strs[0]
        else: 
            return self.getCommonPrefix(strs,0,len(strs)-1)
        
    def getCommonPrefix(self,strs,left,right):
        if left == right:
            return strs[left]
        elif right - left == 1:
            return self.Prefix(strs[left], strs[right])
        else:
            mid = (left + right) // 2
            astr = self.getCommonPrefix(strs, left, mid)
            bstr = self.getCommonPrefix(strs, mid + 1, right)
            return self.Prefix(astr, bstr)
    
    def Prefix(self,str1,str2):
        prefix = ""
        if len(str1)>len(str2):
            tmp=str1
            str1=str2
            str2=tmp
        for i,a in enumerate(str1):
            if a==str2[i]:
                prefix = prefix+a
            else:
                break
                
        return prefix