Longest Common Prefix - Amazon Top Interview Questions


Problem Statement :


Given a list of lowercase alphabet strings words, return the longest common prefix.

Example 1

Input
words = ["anthony", "ant", "antigravity"]

Output
"ant"

Explanation

"ant" is the longest common prefix between the three strings.


Solution :



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                        Solution in C++ :

string solve(vector<string>& words) {
    if (words.size() == 0) {
        return "";
    }

    string common = "";
    for (int i = 0;; i++) {
        for (auto word : words) {
            if (i >= word.size() || word[i] != words[0][i]) {
                return common;
            }
        }
        common += words[0][i];
    }
    return common;
}
                    


                        Solution in Java :

import java.util.*;

class Solution {
    public String solve(String[] words) {
        Arrays.sort(words);
        int n = words.length;
        String s = words[0];
        if (n == 1)
            return s;
        String s1 = words[n - 1];

        StringBuilder res = new StringBuilder();

        for (int i = 0; i < Math.min(s1.length(), s.length()); i++) {
            if (s.charAt(i) == s1.charAt(i))
                res.append(s.charAt(i));
            else
                break;
        }
        return res.toString();
    }
}
                    


                        Solution in Python : 
                            
class Solution:
    def solve(self, words):

        # O(n) to find shortest word
        min_word = min(words, key=len, default="")

        # O(m*n) m is number of characters in minimum word
        prefix_len = 0
        for idx, char in enumerate(min_word):
            for word in words:
                if word[idx] != char:
                    return min_word[:prefix_len] if prefix_len else ""

                else:
                    continue

            prefix_len += 1

        return min_word[:prefix_len] if prefix_len else ""


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