Longest Common Prefix

Question

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: Input: strs = ["flower","flow","flight"] Output: "fl" I'm new in coding and try to solve this problem (from leetcode). my way is search the shortest string between strings, here is my code, I can't figure out where did I do wrong, it seems the while loop doesn't work at all. I appreciate if someone could help me. here is my code:

class Solution:
    def longestCommonPrefix(self, strs: List[str]) -> str:
        string = ""
        len_st = []
        for st in strs:
            len_st.append(len(st))
        m = min(len_st)
        prefix = strs[len_st.index(m)]
        while prefix:
            for st in strs:
                if prefix in st:
                    continue
                else:
                    prefix = prefix.replace(prefix[-1], "")
                break
            return prefix
        else:
            return ""

input : ["flower","flow","flight"] output: "flo" expected output: "fl"

Answer 1

Approach:

1. First, we will find the shortest string and its length.
2. Secondly, we will take the first string and match each character with the other strings.
3. As soon as we encounter a character that does not fit, we will break out of the loop.

Code Solution :

    public String longestCommonPrefix(String[] strs) {
        // Longest common prefix string
        StringBuilder longestCommonPrefix = new StringBuilder();
        // Base condition
        if (strs == null || strs.length == 0) {
            return longestCommonPrefix.toString();
        }
        // Find the minimum length string from the array
        int minimumLength = strs[0].length();
        for (int i = 1; i < strs.length; i++) {
            minimumLength = Math.min(minimumLength, strs[i].length());
        }
        // Loop for the minimum length
        for (int i = 0; i < minimumLength; i++) {
            // Get the current character from first string
            char current = strs[0].charAt(i);
            // Check if this character is found in all other strings or not
            for (String str : strs) {
                if (str.charAt(i) != current) {
                    return longestCommonPrefix.toString();
                }
            }
            longestCommonPrefix.append(current);
        }
        return longestCommonPrefix.toString();
    }
}

Time Complexity : O(m*n)

Space Complexity : O(1)