1263B - PIN Codes - CodeForces Solution

// Author: MAMUN MIAH
// Date:23 February 2023
// Link:

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

#define endl "\n"
#define ll long long
#define pb push_back
void solve()
{
    int n;
    cin >> n;
    string pin;
    vector<int> check(10, 0);
    vector<string> keep;
    int ans = 0, dup = n;
    while (n--)
    {
        cin >> pin;
        check[pin[0] - '0'] = 1;
        keep.pb(pin);
    }
    for(int i = 0; i < dup; i++)
    {
        for(int j = i + 1; j < dup; j++)
        {
            if(keep[i] == keep[j])
            {
                ans++;
                for(int k = 0; k <= 9; k++)
                {
                    if(!check[k])
                    {
                        keep[i][0] = '0' + k;
                        check[k] = 1;
                        break;
                    }
                }
                break;
            }
        }
    }
   
    cout << ans << endl;
    for (auto x : keep)
    {
        cout << x << endl;
    }
}
int main()
{
    ios_base ::sync_with_stdio(false);
    cin.tie(nullptr);
    int test;
    test = 1;
    if (true)
    {
        cin >> test;
    }

    while (test--)
    {
        solve();
    }
}