Language: C++

#include"bits/stdc++.h"
using namespace std;
typedef unsigned long long ll;


using Graph=vector<vector<int>>;//グラフ型
void dfs(const Graph &G,int v/*根*/,vector<bool> &seen){
    seen[v]=true;  //vを訪問済にする
    for(auto next_v:G[v]){ //訪問済にしたvとつながっている場所を順番に探す
        if(seen[next_v]) continue; //もし探索済みならスルー
        dfs(G,next_v,seen); //再帰的に探索
    }
}

void bfs(const Graph &G,queue<int> &que/*発見したが訪問はしていない*/,vector<int> &dist/*開始地点からの距離*/){
    while(!que.empty()){
        int v=que.front();//queのうち先頭のものからスタート
        que.pop();//先頭を削除

        for(int nv :G[v]){//vとつながっている点を列挙
            if(dist[nv]!=-1) continue;//発見済(=距離が格納されている)であればスルー
            dist[nv]=dist[v]+1;//vとつながっている点に距離の情報を追加
            que.push(nv);//vとつながっている点を発見済にする
        }
    }
}

string swap_s(string &s){
    for(int i=0;i<s.length()/2;++i){
        swap(s[i],s[s.length()-i-1]);
    }
    return s;
}

int main(void){
    string s,c;
    int q,t,f;
    bool turn=false;
    cin>>s>>q;
    deque<char> d;

    for(int i=0;i<s.length();++i){
        d.push_back(s[i]);
    }
    for(int i=0;i<q;++i){
        cin>>t;
        if(t==1){
            turn=!turn;
        }
        else{
            cin>>f>>c;
            if(f==1){
                if(turn)d.push_back(c);
                else d.push_front(c);
            }
            else{
                if(turn)d.push_front(c);
                else d.push_back(c);
            }
        }
    }
    
    if(turn){
        for(int i=s.length()-1;i>=0;--i){
            cout<<s[i];
        }
    }
    else{
        cout<<s;
    }
}


Compiler output:
a.cc: In function 'int main()':
a.cc:53:36: error: no matching function for call to 'std::deque<char>::push_back(std::string&)'
   53 |                 if(turn)d.push_back(c);
      |                         ~~~~~~~~~~~^~~
In file included from /usr/include/c++/14/deque:66,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:139,
                 from a.cc:1:
/usr/include/c++/14/bits/stl_deque.h:1538:7: note: candidate: 'void std::deque<_Tp, _Alloc>::push_back(const value_type&) [with _Tp = char; _Alloc = std::allocator<char>; value_type = char]'
 1538 |       push_back(const value_type& __x)
      |       ^~~~~~~~~
/usr/include/c++/14/bits/stl_deque.h:1538:35: note:   no known conversion for argument 1 from 'std::string' {aka 'std::__cxx11::basic_string<char>'} to 'const std::deque<char>::value_type&' {aka 'const char&'}
 1538 |       push_back(const value_type& __x)
      |                 ~~~~~~~~~~~~~~~~~~^~~
/usr/include/c++/14/bits/stl_deque.h:1553:7: note: candidate: 'void std::deque<_Tp, _Alloc>::push_back(value_type&&) [with _Tp = char; _Alloc = std::allocator<char>; value_type = char]'
 1553 |       push_back(value_type&& __x)
      |       ^~~~~~~~~
/usr/include/c++/14/bits/stl_deque.h:1553:30: note:   no known conversion for argument 1 from 'std::string' {aka 'std::__cxx11::basic_string<char>'} to 'std::deque<char>::value_type&&' {aka 'char&&'}
 1553 |       push_back(value_type&& __x)
      |                 ~~~~~~~~~~~~~^~~
a.cc:54:34: error: no matching function for call to 'std::deque<char>::push_front(std::string&)'
   54 |                 else d.push_front(c);
      |                      ~~~~~~~~~~~~^~~
/usr/include/c++/14/bits/stl_deque.h:1501:7: note: candidate: 'void std::deque<_Tp, _Alloc>::push_front(const value_type&) [with _Tp = char; _Alloc = std::allocator<char>; value_type = char]'
 1501 |       push_front(const value_type& __x)
      |       ^~~~~~~~~~
/usr/include/c++/14/bits/stl_deque.h:1501:36: note:   no known conversion for argument 1 from 'std::string' {aka 'std::__cxx11::basic_string<char>'} to 'const std::deque<char>::value_type&' {aka 'const char&'}
 1501 |       push_front(const value_type& __x)
      |                  ~~~~~~~~~~~~~~~~~~^~~
/usr/include/c++/14/bits/stl_deque.h:1516:7: note: candidate: 'void std::deque<_Tp, _Alloc>::push_front(value_type&&) [with _Tp = char; _Alloc = std::allocator<char>; value_type = char]'
 1516 |       push_front(value_type&& __x)
      |       ^~~~~~~~~~
/usr/include/c++/14/bits/stl_deque.h:1516:31: note:   no known conversion for argument 1 from 'std::string' {aka 'std::__cxx11::basic_string<char>'} to 'std::deque<char>::value_type&&' {aka 'char&&'}
 1516 |       push_front(value_type&& __x)
      |                  ~~~~~~~~~~~~~^~~
a.cc:57:37: error: no matching function for call to 'std::deque<char>::push_front(std::string&)'
   57 |                 if(turn)d.push_front(c);
      |                         ~~~~~~~~~~~~^~~
/usr/include/c++/14/bits/stl_deque.h:1501:7: note: candidate: 'void std::deque<_Tp, _Alloc>::push_front(const value_type&) [with _Tp = char; _Alloc = std::allocator<char>; value_type = char]'
 1501 |       push_front(const value_type& __x)
      |       ^~~~~~~~~~
/usr/include/c++/14/bits/stl_deque.h:1501:36: note:   no known conversion for argument 1 from 'std::string' {aka 'std::__cxx11::basic_string<char>'} to 'const std::deque<char>::value_type&' {aka 'const char&'}
 1501 |       push_front(const value_type& __x)
      |                  ~~~~~~~~~~~~~~~~~~^~~
/usr/include/c++/14/bits/stl_deque.h:1516:7: note: candidate: 'void std::deque<_Tp, _Alloc>::push_front(value_type&&) [with _Tp = char; _Alloc = std::allocator<char>; value_type = char]'
 1516 |       push_front(value_type&& __x)
      |       ^~~~~~~~~~
/usr/include/c++/14/bits/stl_deque.h:1516:31: note:   no known conversion for argument 1 from 'std::string' {aka 'std::__cxx11::basic_string<char>'} to 'std::deque<char>::value_type&&' {aka 'char&&'}
 1516 |       push_front(value_type&& __x)
      |                  ~~~~~~~~~~~~~^~~
a.cc:58:33: error: no matching function for call to 'std::deque<char>::push_back(std::string&)'
   58 |                 else d.push_back(c);
      |                      ~~~~~~~~~~~^~~
/usr/include/c++/14/bits/stl_deque.h:1538:7: note: candidate: 'void std::deque<_Tp, _Alloc>::push_back(const value_type&) [with _Tp = char; _Alloc = std::allocator<char>; value_type = char]'
 1538 |       push_back(const value_type& __x)
      |       ^~~~~~~~~
/usr/include/c++/14/bits/stl_deque.h:1538:35: note:   no known conversion for argument 1 from 'std::string' {aka 'std::__cxx11::basic_string<char>'} to 'const std::deque<char>::value_type&' {aka 'const char&'}
 1538 |       push_back(const value_type& __x)
      |                 ~~~~~~~~~~~~~~~~~~^~~
/usr/include/c++/14/bits/stl_deque.h:1553:7: note: candidate: 'void std::deque<_Tp, _Alloc>::push_back(value_type&&) [with _Tp = char; _Alloc = std::allocator<char>; value_type = char]'
 1553 |       push_back(value_type&& __x)
      |       ^~~~~~~~~
/usr/include/c++/14/bits/stl_deque.h:1553:30: note:   no known conversion for argument 1 from 'std::string' {aka 'std::__cxx11::basic_string<char>'} to 'std::deque<char>::value_type&&' {aka 'char&&'}
 1553 |       push_back(value_type&& __x)
      |                 ~~~~~~~~~~~~~^~~