Lista

input/code.cpp: In function 'int main()':
input/code.cpp:28:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i = 1; i < first.length(); ++i){
                    ~~^~~~~~~~~~~~~~~~
input/code.cpp:50:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         if(pre.length() > cl){
            ~~~~~~~~~~~~~^~~~
input/code.cpp:54:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         if(cl > pre.length()){
            ~~~^~~~~~~~~~~~~~
input/code.cpp:38:14: warning: unused variable 'lz' [-Wunused-variable]
         bool lz = 1;
              ^~

#include <iostream>
#include <vector>
#include <string>

using namespace std;
using ll = long long;

void gg(){
    cout << "IMPOSSIBLE\n";
    exit(0);
}

int dig_at_pos(int num, int pos){
    while(pos--)num/=10;
    return num%10;
}

int main(){

    int n;
    cin >> n;
    vector<string> a(n);
    for(auto& x : a){
        cin >> x;
    }
    string first = a[0];
    if(first[0] == '?')first[0] = '1';
    for(int i = 1; i < first.length(); ++i){
        if(first[i] == '?')first[i] = '0';
    }
    //cout << first << "\n";
    a[0] = first;

    for(int k = 1; k < n; ++k){

        //cout << k << "\n";
        
        bool lz = 1;
        bool tight = 1;

        string pre = a[k-1];
        string cur = a[k];
        string now = "";
        //cout << pre << " " << cur << "\n";
        //cout << pre << " " << cur << "\n";

        int cl  = cur.length();
        //cout << cl << "\n";

        if(pre.length() > cl){
            //cout << "kek\n" << pre << "\n";
            gg();
        }
        if(cl > pre.length()){
            for(int i = 0; i < cl; ++i){
                if(cur[i] == '?')now += '0' + (i == 0);
                else now += cur[i];
            }
        }

        else{
            for(int i = 0; i < cl; ++i){
                //cout << now << "\n";
                char add = 'x';
                if(pre[i] == cur[i])add=cur[i];
                else if(pre[i] > cur[i] && cur[i] != '?' && tight){
                    //cout << "hah\n";
                    gg();
                }
                else if(pre[i] > cur[i] && cur[i] != '?' && !tight)add=cur[i];
                else if(cur[i] > pre[i] && cur[i] != '?')tight = 0, add=cur[i];
                else if(cur[i]=='?'){

                    if(!tight){
                        add = ('0' + (i == 0));
                    }

                    else{

                        bool ok = 0;
                        for(int j = i + 1; j < cl; ++j){
                            if(cur[j] > pre[j] && cur[j] != '?'){
                                ok = 1;
                                break;
                            }
                            if(cur[j] == '?'){
                                if(pre[j] == '9')continue;
                                ok = 1;
                                break;
                            }
                            break;
                        }

                        if(!ok && pre[i] == '9'){
                            gg();
                        }

                        else{
                            if(ok)add = pre[i];
                            else{
                                //cout << "hah\n";
                                add = pre[i] + 1;
                                tight = 0;
                            }
                        }
                    }
                }
                //cout << add << " ";
                now += add;
            }
        }
        //cout << "\n" << now << "\n";
        a[k] = now;
    }

    for(int i = 0; i < n; ++i){
        cout << a[i] << "\n";
    }
}

Test 1

Group: 1, 2, 3

Verdict: ACCEPTED

Test 2

Group: 2, 3

Verdict: WRONG ANSWER

Test 3

Group: 3

Verdict: WRONG ANSWER

Test 4

Group: 1, 2, 3

Verdict: ACCEPTED

Test 5

Group: 1, 2, 3

Verdict: ACCEPTED

Test 6

Group: 1, 2, 3

Verdict: WRONG ANSWER

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