Longest Common Prefix in C, C++, Java & Python – Code with Explanation & Examples in Short and Simple

   

C Program

#include <stdio.h>
#include <string.h>

char* longestCommonPrefix(char arr[][100], int n) {
    static char prefix[100];
    strcpy(prefix, arr[0]);

    for(int i = 1; i < n; i++) {
        int j = 0;
        while(prefix[j] && arr[i][j] && prefix[j] == arr[i][j])
            j++;
        prefix[j] = '\0';
    }
    return prefix;
}

int main() {
    char arr[4][100] = {"flower", "flow", "flight", "flute"};
    printf("Longest Common Prefix: %s\n", longestCommonPrefix(arr, 4));
    return 0;
}

C Output

Longest Common Prefix: fl

C++ Program

#include <iostream>
#include <vector>
using namespace std;

string longestCommonPrefix(vector<string>& strs) {
    string prefix = strs[0];
    for (int i = 1; i < strs.size(); i++) {
        int j = 0;
        while (j < prefix.size() && j < strs[i].size() && prefix[j] == strs[i][j])
            j++;
        prefix = prefix.substr(0, j);
    }
    return prefix;
}

int main() {
    vector<string> strs = {"interview", "internet", "internal", "into"};
    cout << "Longest Common Prefix: " << longestCommonPrefix(strs) << endl;
    return 0;
}

C++ Output

Longest Common Prefix: int

JAVA Program

class Main {
    public static String longestCommonPrefix(String[] strs) {
        String prefix = strs[0];
        for (int i = 1; i < strs.length; i++) {
            int j = 0;
            while (j < prefix.length() && j < strs[i].length() &&
                   prefix.charAt(j) == strs[i].charAt(j)) {
                j++;
            }
            prefix = prefix.substring(0, j);
        }
        return prefix;
    }

    public static void main(String[] args) {
        String[] strs = {"coding", "code", "coder", "codex"};
        System.out.println("Longest Common Prefix: " + longestCommonPrefix(strs));
    }
}

JAVA Output

Longest Common Prefix: cod

Python Program

def longest_common_prefix(strs):
    prefix = strs[0]
    for i in range(1, len(strs)):
        j = 0
        while j < len(prefix) and j < len(strs[i]) and prefix[j] == strs[i][j]:
            j += 1
        prefix = prefix[:j]
    return prefix

words = ["apple", "application", "appetite", "apply"]
print("Longest Common Prefix:", longest_common_prefix(words))

Python Output

Longest Common Prefix: appl

In-Depth Explanation

Example

Take the words [\"flower\", "flow", "flight", "flute"]. The shared starting part is "fl". That is the longest letter sequence at the beginning that they have. As soon as there is a mismatch (such as "o" in "flow" versus "i" in "flight"), we quit.

Real-Life Analogy

Consider friends singing a song in unison. Initially, all are synchronized and sing the same lyrics, but after some time, one starts singing a different line. The part they sang in harmony before moving out of sync is similar to the longest common prefix.

Another analogy: Picture addresses. Suppose two friends reside at "123 Main Street, New York" and "123 Main Street, New Jersey." They share a common prefix, "123 Main Street, New." Then they branch out.

Why It Matters

The longest common prefix is a concept that appears in various applications in real life. It is commonly utilized in coding in applications such as autocomplete in Google search or IDEs where input of only a few characters provides a list of matching words. It is also utilized in genome sequencing in bioinformatics where frequent DNA patterns must be located. It is also used in data compression (such as LCP arrays in suffix arrays).

From the point of view of an interview, this issue is highly typical in FAANG-typen coding interviews since it checks string manipulation, iteration, prefix ideas, and attentive boundary conditions. It looks easy but makes you think about solving the problem step by step.

Learning Insights

By doing this, one learns how to compare strings character by character, how to shrink the search space gradually, and how to deal with mismatches. New programmers also learn about the significance of substring operations and traversing arrays. It teaches efficiency since searching until the length of the shortest string is sufficient. 

Edge Cases

If the list contains one word only, the prefix is the word itself.

If no letters correspond, the prefix is the empty string "".

Extremely big inputs test performance—O(N * M) where N is the number of words and M is the length of the shortest word.

SEO-Friendly Insight

The longest common prefix question is one of the frequently asked coding interview questions for beginners in companies such as Amazon, Google, and Infosys. Solving this question assists students in improving string manipulation capabilities and equipping themselves with practical applications such as autocomplete, searching optimization, and pattern detection in big data. Solving this question enhances problem-solving abilities, increases logical thinking, and makes beginners comfortable with string-based programming problems.