Language: C++

#include <bits/stdc++.h>
#ifdef __LOCAL
    #define DBG(X) cout << #X << " = " << (X) << endl;
    #define SAY(X) cout << (X) << endl;
    #include <filesystem>
    namespace fs = std::filesystem;
#else
    #define DBG(X)
    #define SAY(X)
#endif

using namespace std;

using ll = long long int;
using ull = unsigned long long int;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;

int dx[]={1, 0, -1, 0, 1,-1, 1,-1};
int dy[]={0, 1, 0, -1, 1, 1,-1,-1};
const int INT_INF = (int)(2e9);
const ll  LL_INF = (ll)(2e18);
static mt19937 _g(time(nullptr));
 
inline ll randint(ll a, ll b) { ll w = (_g() << 31LL) ^ _g(); return a + w % (b - a + 1); }
inline void fast_io() { ios_base::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr); };
template<typename T, typename S> inline ostream& operator<<(ostream& os, const pair<T, S> p) { cout << "[" << p.first << ";" << p.second << "]"; return os; }
template<typename T, typename S> inline ostream& operator<<(ostream& os, const map<T, S> p) { for (auto el : p) cout << "[" << el.first << ";" << el.second << "]"; return os; }
template<typename T> inline ostream& operator<<(ostream& os, const vector<T>& v) { for (auto el : v) cout << el << " "; return os; }
template<typename T> inline vector<T> fetch_vec(int sz) { vector<T> ret(sz); for (auto& elem : ret) cin >> elem; return ret; }

int N;
ll A,B,C;
vector<string> S;
void input(){
    fast_io();
    #ifdef __LOCAL
        fs::path __p = __FILE__;
        fs::path __input, __output;
        __input = __output = __p.parent_path();
        __input += string("/input/") + string(__p.stem()) + string(".txt");
        __output += string("/output/") + string(__p.stem()) + string(".txt");
        freopen(__input.c_str(), "r", stdin);
        freopen(__output.c_str(), "w", stdout);
    #endif
    cin >> N >> A >> B >> C;
    for (int i = 0; i < N; i++)
    {
        string s; cin >> s;
        S.push_back(s);
    }    
}

void back(int i,vector<char> &ans){
    string last = ans.back();
    ans.pop_back();
    if(S[i-1]=="BC" && last=="C"){
        ans.push_back('B');
        B++,C--;
        B++,C--;
    }
    if(S[i-1]=="BC" && last=="B"){
        ans.push_back('C');
        B--,C++;
        B--,C++;
    }
    if(S[i-1]=="AB" && last=="B"){
        ans.push_back('A');
        B--,A++;
        B--,A++;
    }
    if(S[i-1]=="AB" && last=="A"){
        ans.push_back('B');
        B++,A--;
        B++,A--;
    }
    if(S[i-1]=="AC" && last=="A"){
        ans.push_back('C');
        C++,A--;
        C++,A--;
    }
    if(S[i-1]=="AC" && last=="C"){
        ans.push_back('A');
        C--,A++;
        C--,A++;
    }
}

int solve(){
    if(A==0 && B==0 && C==0){
        cout << "No" << endl;
        return 0;
    }
    if(A==0 && B==0 && S[0]=="AB"){
        cout << "No" << endl;
        return 0;
    }
    if(C==0 && B==0 && S[0]=="BC"){
        cout << "No" << endl;
        return 0;
    }
    if(A==0 && C==0 && S[0]=="AC"){
        cout << "No" << endl;
        return 0;
    }
    // 以下すべてYES
    vector<char> ans;
    for (int i = 0; i < N; i++)
    {
        if(S[i]=="AB"){
            if(A==0 && B==0){
                back(i,ans);
            }
            if(B>A){
                ans.push_back('A');
                A++,B--;
            }
            else{
                ans.push_back('B');
                A--,B++;
            }
        }
        if(S[i]=="BC"){
            if(C==0 && B==0){
                back(i,ans);
            }
            if(C>B){
                ans.push_back('B');
                B++,C--;
            }
            else{
                ans.push_back('C');
                B--,C++;
            }
        }
        if(S[i]=="AC"){
            if(C==0 && A==0){
                back(i,ans);
            }
            if(C>A){
                ans.push_back('A');
                A++,C--;
            }
            else{
                ans.push_back('C');
                A--,C++;
            }
        }
        // printf("%d %d %d\n",A,B,C);
    }
    
    cout << "Yes" << endl;
    for(auto a:ans) cout << a << "\n";
    return 0;
}   

int main()
{
    input();
    solve();
    return 0;
}


Compiler output:
a.cc: In function 'void back(int, std::vector<char>&)':
a.cc:56:27: error: conversion from '__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type' {aka 'char'} to non-scalar type 'std::string' {aka 'std::__cxx11::basic_string<char>'} requested
   56 |     string last = ans.back();
      |                   ~~~~~~~~^~