Largest Concatenated Number

large_concat_num.cpp

// Problem Link: https://practice.geeksforgeeks.org/problems/largest-number-formed-from-an-array/0

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

#define ull uint64_t

void largestConcatenatedNumber(vector<string> &nums) {
    sort(nums.begin(), nums.end(), 
        [](string X, string Y){
            string XY = X.append(Y);
            string YX = Y.append(X);
            return (XY.compare(YX) < 0 ? 0 : 1);
        });
    
    for(ull i = 0; i < nums.size(); ++i)
        cout << nums[i];
    
    cout << endl;
}

int main() {
    int t;  cin >> t;
    while(t--) {
        int n;  cin >> n;
        
        vector<string> nums(n);
        for(int i = 0; i < n; ++i)
            cin >> nums[i];
            
        largestConcatenatedNumber(nums);
    }
    return 0;
}