Language: C++

#include <vector>
#include <iostream>
#include <cmath>
#include <map>
#include <unordered_map>
#include <algorithm>
#include <fstream>
#include <unistd.h>
#include <string.h>
#include <string>
#include <numeric>
#include <queue>
#include <deque>
#include <sstream>
#include <iomanip>
#include <set>
#include <stack>
#include <cassert>
#include <functional>
#include <random>
using namespace std;
typedef int64_t ll;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<vvl> vvvl;
typedef vector<vvvl> vvvvl;
typedef vector<vi> vvi;
typedef vector<vvi> vvvi;
typedef vector<bool> vb;
typedef vector<vector<bool>> vvb;
typedef vector<vvb> vvvb;
typedef vector<vvvb> vvvvb;
typedef vector<string> vs;
typedef vector<vs> vvs;
typedef vector<vvs> vvvs;
typedef vector<char> vc;
typedef vector<vector<char>> vvc;
typedef vector<double> vd;
typedef vector<vd> vvd;
typedef vector<vvd> vvvd;
typedef unordered_map<ll, ll> uii;
typedef unordered_map<ll, ll> uuii;
typedef unordered_map<ll, ll> uuuii;
typedef long double LD;
typedef vector<LD> vld;
typedef vector<pair<LD, LD>> vpld;
typedef pair<ll, ll> PL;
typedef vector<PL> vpl;
typedef vector<vector<PL>> vvpl;
typedef vector<vvpl> vvvpl;
typedef pair<ll, PL> TL;
typedef vector<TL> vtl;
typedef vector<vtl> vvtl;
typedef long double ld;
typedef vector<ld> vld;
const ll LINF = 1e17;
const long double pi = 3.1415926535897932;
const string endstr = "\n";
#define FOR(i, a, b) for(ll i = (a); i < b; i++)
#define RFOR(i, a, b) for(ll i = (a); i > b; i--)
#define rep(i, n) for(ll i = 0; i < n; i++)
#define rrep(i, n) for(ll i = n-1; i > -1; i--)
#define FORMAP(it, m) for(auto it = m.begin(); it != m.end(); it++)
#define ff first
#define ss second
#define pb push_back
#define epb emplace_back
#define ALL(X) (X).begin(),(X).end()

template <typename T> T gcd(T a, T b) {return (a == 0) ? b : gcd(b%a, a);}
template <typename T> T lcm(T a, T b) { return a / gcd(a, b) * b;}

bool p_comp_fs(const PL p1, const PL p2){ return p1.first < p2.first;};
bool p_comp_fg(const PL p1, const PL p2){ return p1.first > p2.first;};
bool p_comp_ss(const PL p1, const PL p2){ return p1.second < p2.second;};
bool p_comp_sg(const PL p1, const PL p2){ return p1.second > p2.second;};
template <typename T>
vector<T> uniquen(vector<T> vec /* copy */){
    sort(ALL(vec)); vec.erase(unique(vec.begin(), vec.end()), vec.end()); return vec;
}

inline ll popcnt(ll x){return __builtin_popcountll((unsigned long long)x);};
template<class T> bool chmax(T &a, T b) { if (a < b) { a = b; return true; } return false; }
template<class T> bool chmin(T &a, T b) { if (a > b) { a = b; return true; } return false; }
//friend bool operator<(const tpl& lhs, const tpl& rhs){
//    return std::tie(lhs.l, lhs.r) < std::tie(rhs.l, rhs.r);
//}

bool bit(ll st, ll b){return ((st>>b)&1) == 1;}

ll N;


void dfs(ll x, ll& ans){
    if(x == 0) return;
    
    ll d = 0, u = 0, cur = 1;
    rep(i, 40){
        if(i%2 == 0){
            u += cur;
        }
        else{
            d -= cur;
        }
        
        if(d <= x && x <= u){
            ans |= 1ll << i;
            x -= i%2 == 0 ? cur : -cur;
            dfs(x, ans);
            break;
        }
        cur *= 2;
    }
}

int main(){
#ifdef __DEBUG_LOCAL__
    ifstream file("../../../../../in.txt"); if(file.is_open()) cin.rdbuf(file.rdbuf());
#endif
    ios_base::sync_with_stdio(false); cin.tie(nullptr);
    
    cin >> N;
    if(N == 0){
        cout << 0 << endstr; return 0;
    }
    
    ll ans = 0;
    dfs(N, ans);
    string ans_str = bitset<64>(ans).to_string();
    deque<char> dq;
    rep(i, ans_str.size()) dq.push_back(ans_str[i]);
    
    
    while(dq.size() > 0){
        if(dq.front() == '0') dq.pop_front();
        else{
            break;
        }
    }
    for(char c : dq) cout << c;
    cout << endstr;
    
    return 0;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:130:22: error: 'bitset' was not declared in this scope
  130 |     string ans_str = bitset<64>(ans).to_string();
      |                      ^~~~~~
a.cc:21:1: note: 'std::bitset' is defined in header '<bitset>'; this is probably fixable by adding '#include <bitset>'
   20 | #include <random>
  +++ |+#include <bitset>
   21 | using namespace std;
a.cc:130:38: error: request for member 'to_string' in 'ans', which is of non-class type 'll' {aka 'long int'}
  130 |     string ans_str = bitset<64>(ans).to_string();
      |                                      ^~~~~~~~~