longest-common-prefix

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: ["flower","flow","flight"]
Output: "fl"
Example 2:

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

All given inputs are in lowercase letters a-z.

My code:
class Solution:
    def longestCommonPrefix(self, strs):
        """
        :type strs: List[str]
        :rtype: str
        """
        if len(strs)==0:
            return ""
        final_str=""
        j=0
        length=10000000
        for i in range(len(strs)):
            if length>len(strs[i]):
                length=len(strs[i])
        while j<length:
            flag=True
            for i in range(len(strs)):
                tmp_str=strs[i]
                if j>=len(strs[i]):
                    break
                if i==0:
                    check_str=tmp_str[j]
                    continue
                if check_str!=tmp_str[j]:
                    flag=False
            if flag==True:
                final_str=final_str+tmp_str[j]
            else:
                 break   
            j=j+1
        return final_str
            
            
            
        
Solution:
https://leetcode.com/problems/longest-common-prefix/