Freight trains

input/code.cpp: In function 'int comp(std::string&, std::string&)':
input/code.cpp:40:21: warning: comparison of integer expressions of different signedness: 'int' and 'size_t' {aka 'long unsigned int'} [-Wsign-compare]
   40 |   for (int i = 0; i < length_a + length_b; i++) {
      |                   ~~^~~~~~~~~~~~~~~~~~~~~
input/code.cpp:41:22: warning: comparison of integer expressions of different signedness: 'int' and 'size_t' {aka 'long unsigned int'} [-Wsign-compare]
   41 |     char char_a = (i < length_a) ? a[i] : b[i - length_a];
      |                    ~~^~~~~~~~~~
input/code.cpp:42:22: warning: comparison of integer expressions of different signedness: 'int' and 'size_t' {aka 'long unsigned int'} [-Wsign-compare]
   42 |     char char_b = (i < length_b) ? b[i] : a[i - length_b];
      |                    ~~^~~~~~~~~~

#include <bits/stdc++.h>
using namespace std;

#define PRINT_ARR(arr, n)                                                      \
  do {                                                                         \
    for (int i = 0; i < n; i++) {                                              \
      cout << arr[i] << " ";                                                   \
    }                                                                          \
    cout << "\n";                                                              \
  } while (0)

typedef long long ll;

// int cmp(string a, string b, string c) {
//   int i =0;
//   if (a.size() < 2 && b.size() < 2) {
//     return
//   }
//   while (i < a.size() && i < b.size() && a[i] == b[i])
//     i++;
//   if (a[i-1] != b[i-1])
//
// }
int cmp(string &a, string &b) {
  size_t la = a.length();
  size_t lb = b.length();
  size_t i = 0;
  size_t ll = min(la, lb);
  while (i < ll && a[i] == b[i])
    i++;
  if (i < ll) {
    return a[i] < b[i];
  }
  return la > lb;
}

int comp(string &a, string &b) {
  size_t length_a = a.length();
  size_t length_b = b.length();
  for (int i = 0; i < length_a + length_b; i++) {
    char char_a = (i < length_a) ? a[i] : b[i - length_a];
    char char_b = (i < length_b) ? b[i] : a[i - length_b];
    if (char_a < char_b) {
      return true;
    } else if (char_a > char_b) {
      return false;
    }
  }
  return false;
}

int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);

  int n;
  cin >> n;

  vector<string> arr(n);
  string t;
  if (n == 1) {
    cin >> t;
    cout << t << endl;
    return 0;
  }

  for (int i = 0; i < n; i++) {
    cin >> arr[i];
  }

  sort(arr.begin(), arr.end(), cmp);

  // PRINT_ARR(arr, n);

  int l = 0, r = 1;
  while (l < n && r < n) {
    if (comp(arr[l], arr[r])) {
      cout << arr[l];
      l = max(l, r) + 1;
    } else {
      cout << arr[r];
      r = max(l, r) + 1;
    }
  }
  cout << arr[min(l, r)] << endl;

}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED

Test 14

Verdict: ACCEPTED

Test 15

Verdict: ACCEPTED

Test 16

Verdict: ACCEPTED

Test 17

Verdict: ACCEPTED

Test 18

Verdict: ACCEPTED

Test 19

Verdict: ACCEPTED

Test 20

Verdict: ACCEPTED

Test 21

Verdict: ACCEPTED

Test 22

Verdict: ACCEPTED

Test 23

Verdict: ACCEPTED

Test 24

Verdict: ACCEPTED

Test 25

Verdict: ACCEPTED

Test 26

Verdict: ACCEPTED

Test 27

Verdict: ACCEPTED

Test 28

Verdict: ACCEPTED

Test 29

Verdict: ACCEPTED

Test 30

Verdict: ACCEPTED

Test 31

Verdict: ACCEPTED

Test 32

Verdict: WRONG ANSWER

Test 33

Verdict: WRONG ANSWER

Test 34

Verdict: WRONG ANSWER

Test 35

Verdict: WRONG ANSWER

Test 36

Verdict: WRONG ANSWER

Test 37

Verdict: WRONG ANSWER

Test 38

Verdict: WRONG ANSWER

Test 39

Verdict: WRONG ANSWER

Test 40

Verdict: WRONG ANSWER

Test 41

Verdict: WRONG ANSWER

Test 42

Verdict: WRONG ANSWER

Test 43

Verdict: WRONG ANSWER

Test 44

Verdict: WRONG ANSWER

Test 45

Verdict: WRONG ANSWER

Test 46

Verdict: WRONG ANSWER

Test 47

Verdict: WRONG ANSWER

Test 48

Verdict: WRONG ANSWER

Test 49

Verdict: WRONG ANSWER

Test 50

Verdict: WRONG ANSWER

Test 51

Verdict: WRONG ANSWER

Test 52

Verdict: WRONG ANSWER

Test 53

Verdict: WRONG ANSWER

Test 54

Verdict: WRONG ANSWER

Test 55

Verdict: WRONG ANSWER

Test 56

Verdict: WRONG ANSWER

Test 57

Verdict: WRONG ANSWER

Test 58

Verdict: WRONG ANSWER

Test 59

Verdict: WRONG ANSWER

Test 60

Verdict: WRONG ANSWER

Test 61

Verdict: WRONG ANSWER

Test 62

Verdict: WRONG ANSWER

Test 63

Verdict: WRONG ANSWER

Test 64

Verdict: WRONG ANSWER

Test 65

Verdict: WRONG ANSWER

Test 66

Verdict: WRONG ANSWER

Test 67

Verdict: WRONG ANSWER

Test 68

Verdict: WRONG ANSWER

Test 69

Verdict: WRONG ANSWER

Test 70

Verdict: WRONG ANSWER

Test 71

Verdict: WRONG ANSWER