Lista

input/code.cpp: In function 'int main()':
input/code.cpp:16:12: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     if (cn > p.size()) {
         ~~~^~~~~~~~~~

#include <bits/stdc++.h>
using namespace std;
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  int n;
  cin >> n;
  string p, s[n];
  for (auto &c : s) {
    cin >> c;
    if (c.size() < p.size()) {
      cout << "IMPOSSIBLE" << endl;
      return 0;
    }
    int cn = (int) c.size();
    if (cn > p.size()) {
      for (int i = 0; i < cn; ++i) {
        if (c[i] == '?') {
          c[i] = '0' + (i == 0);
        }
      }
    } else {
      for (int i = 0; i < cn; ++i) {
        if (c[i] != '?') {
          continue;
        }
        bool f = 0;
        for (int j = i == 0; j <= 9; ++j) {
          c[i] = j + '0';
          auto t = c;
          for (int k = i + 1; k < cn; ++k) {
            if (t[k] == '?') {
              t[k] = '9';
            }
          }
          if (t > p) {
            f = 1;
            break;
          }
        }
        if (!f) {
          cout << "IMPOSSIBLE" << endl;
          return 0;
        }
      }
    }
    if (c.size() == p.size() && c <= p) {
      cout << "IMPOSSIBLE" << endl;
      return 0;
    }
    p = c;
  }
  for (auto &x : s) {
    cout << x << '\n';
  }
}

Test 1

Group: 1, 2, 3

Verdict: ACCEPTED

Test 2

Group: 2, 3

Verdict: ACCEPTED

Test 3

Group: 3

Verdict: ACCEPTED

Test 4

Group: 1, 2, 3

Verdict: ACCEPTED

Test 5

Group: 1, 2, 3

Verdict: ACCEPTED

Test 6

Group: 1, 2, 3

Verdict: ACCEPTED

Test 7

Group: 1, 2, 3

Verdict: ACCEPTED

Test 8

Group: 3

Verdict: ACCEPTED

Test 9

Group: 3

Verdict: ACCEPTED

Test 10

Group: 3

Verdict: ACCEPTED