longestprefix.cpp

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

class Solution {
public:
    string longestCommonPrefix(vector<string>& strs) {
        if (strs.empty()) return ""; // Edge case: Empty input
        
        int prefixLength = 0; // Track common prefix length
        for (int i = 0; i < strs[0].size(); i++) { // Scan column-wise
            char c = strs[0][i]; // First string's character at position i
            for (int j = 1; j < strs.size(); j++) { // Compare with all strings
                if (i >= strs[j].size() || strs[j][i] != c) // Mismatch
                    return buildPrefix(strs[0], prefixLength);
            }
            prefixLength++;
        }
        return buildPrefix(strs[0], prefixLength); // If no mismatches, return full prefix
    }

private:
    string buildPrefix(const string& str, int length) {
        string result;
        for (int i = 0; i < length; i++) {
            result += str[i]; // Manually construct the prefix
        }
        return result;
    }
};

// **Main function to test locally**
int main() {
    Solution sol;
    int n;
    cin >> n; // Number of strings
    vector<string> strs(n);
    for (int i = 0; i < n; i++) {
        cin >> strs[i];
    }
    cout << sol.longestCommonPrefix(strs) << endl;
    return 0;
}