Problem p03091 (C++)

Buggy submission (status: Time Limit Exceeded):
/**
 * code generated by JHelper
 * More info: https://github.com/AlexeyDmitriev/JHelper
 * @author
 */

#include <fstream>
#include <iostream>

#ifndef _TB
#define _TB

#include <bits/stdc++.h>

using namespace std;

#define FOR(i, a, b) for (int i = a; i < b; ++i)
#define RFOR(i, b, a) for (int i = b - 1; i >= a; --i)
#define REP(i, N) FOR(i, 0, N)
#define RREP(i, N) RFOR(i, N, 0)

#define MIN(A, B) ((A) < (B) ? (A) : (B))
#define MAX(A, B) ((A) > (B) ? (A) : (B))
#define ABS(A) ((A) < 0 ? (-(A)) : (A))
#define ALL(V) V.begin(), V.end()
#define SIZE(V) (int)V.size()
#define pb push_back
#define mp make_pair
#define EPS 1e-7
#define Pi 3.14159265358979
#define FILL(a, v) memset(a, v, sizeof(a))

using namespace std;

typedef long long Long;
typedef unsigned long long ULong;
typedef unsigned int Uint;
typedef unsigned char Uchar;
typedef vector<int> VI;
typedef pair<int, int> PII;

#define X first
#define Y second

typedef std::pair<int, int> pii;
typedef long long ll;
typedef unsigned long long ull;
typedef unsigned int ui;
typedef pair<ui, ui> puu;

template <typename T, typename U>
std::istream &operator>>(std::istream &i, pair<T, U> &p) {
  i >> p.X >> p.Y;
  return i;
}
template <typename T> std::istream &operator>>(std::istream &i, vector<T> &t) {
  for (auto &v : t) {
    i >> v;
  }
  return i;
}
template <typename T, typename U>
std::ostream &operator<<(std::ostream &o, const pair<T, U> &p) {
  o << p.X << ' ' << p.Y;
  return o;
}
template <typename T>
std::ostream &operator<<(std::ostream &o, const vector<T> &t) {
  if (t.empty())
    o << '\n';
  for (size_t i = 0; i < t.size(); ++i) {
    o << t[i] << " \n"[i == t.size() - 1];
  }
  return o;
}
template <typename T> using minheap = priority_queue<T, vector<T>, greater<T>>;
template <typename T> using maxheap = priority_queue<T, vector<T>, less<T>>;
template <typename T> bool in(T a, T b, T c) { return a <= b && b < c; }
ui logceil(int x) { return 8 * sizeof(int) - __builtin_clz(x); }

namespace std {
template <typename T, typename U> struct hash<pair<T, U>> {
  hash<T> t;
  hash<U> u;
  size_t operator()(const pair<T, U> &p) const {
    return t(p.x) ^ (u(p.y) << 7);
  }
};
} // namespace std
template <typename T, typename F> T bsh(T l, T h, const F &f) {
  T r = -1, m;
  while (l <= h) {
    m = (l + h) / 2;
    if (f(m)) {
      l = m + 1;
      r = m;
    } else {
      h = m - 1;
    }
  }
  return r;
}
template <typename F>
double bshd(double l, double h, const F &f, double p = 1e-9) {
  ui r = 3 + (ui)log2((h - l) / p);
  while (r--) {
    double m = (l + h) / 2;
    if (f(m)) {
      l = m;
    } else {
      h = m;
    }
  }
  return (l + h) / 2;
}
template <typename T, typename F> T bsl(T l, T h, const F &f) {
  T r = -1, m;
  while (l <= h) {
    m = (l + h) / 2;
    if (f(m)) {
      h = m - 1;
      r = m;
    } else {
      l = m + 1;
    }
  }
  return r;
}
template <typename F>
double bsld(double l, double h, const F &f, double p = 1e-9) {
  ui r = 3 + (ui)log2((h - l) / p);
  while (r--) {
    double m = (l + h) / 2;
    if (f(m)) {
      h = m;
    } else {
      l = m;
    }
  }
  return (l + h) / 2;
}
template <typename T> T gcd(T a, T b) {
  if (a < b)
    swap(a, b);
  return b ? gcd(b, a % b) : a;
}

template <typename T> class vector2 : public vector<vector<T>> {
public:
  vector2() {}
  vector2(size_t a, size_t b, T t = T())
      : vector<vector<T>>(a, vector<T>(b, t)) {}
};
template <typename T> class vector3 : public vector<vector2<T>> {
public:
  vector3() {}
  vector3(size_t a, size_t b, size_t c, T t = T())
      : vector<vector2<T>>(a, vector2<T>(b, c, t)) {}
};
template <typename T> class vector4 : public vector<vector3<T>> {
public:
  vector4() {}
  vector4(size_t a, size_t b, size_t c, size_t d, T t = T())
      : vector<vector3<T>>(a, vector3<T>(b, c, d, t)) {}
};
template <typename T> class vector5 : public vector<vector4<T>> {
public:
  vector5() {}
  vector5(size_t a, size_t b, size_t c, size_t d, size_t e, T t = T())
      : vector<vector4<T>>(a, vector4<T>(b, c, d, e, t)) {}
};

void fastIO() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);
}

#endif

const int MAXN = 100100;

VI g[MAXN];

set<int> v;

int go(int v, int p) {
  if (g[v].size() > 2)
    return v;
  for (auto nv : g[v])
    if (nv != p)
      return go(nv, p);
}

class CThreeCircuits {
public:
  string solve1(std::istream &in) {
    fastIO();
    int n, m;
    in >> n >> m;

    v.clear();

    REP(i, n) { g[i].clear(); }

    int b, c;

    REP(i, m) {
      in >> b >> c;
      --b;
      --c;
      g[b].push_back(c);
      g[c].push_back(b);
    }

    bool bad = false;
    bool has6 = false;

    REP(i, n) {
      if (g[i].size() % 2 == 1)
        bad = true;
      if (g[i].size() >= 4) {
        v.insert(i);
      }
      if (g[i].size() >= 6)
        has6 = true;
    }

    if (bad) {
      return "No";
    }

    int c4 = v.size();

    if (has6 || c4 >= 3) {
      return "Yes";
    }

    if (c4 < 2) {
      return "No";
    }

    int c1 = *v.begin();

    for (auto v : g[c1]) {
      if (go(v, c1) == c1)
        return "Yes";
    }

    return "No";
  }

  void solve(std::istream &in, std::ostream &out) { out << solve1(in) << endl; }
};

int main() {
  CThreeCircuits solver;
  std::istream &in(std::cin);
  std::ostream &out(std::cout);
  solver.solve(in, out);
  return 0;
}


Fixed submission:
/**
 * code generated by JHelper
 * More info: https://github.com/AlexeyDmitriev/JHelper
 * @author
 */

#include <fstream>
#include <iostream>

#ifndef _TB
#define _TB

#include <bits/stdc++.h>

using namespace std;

#define FOR(i, a, b) for (int i = a; i < b; ++i)
#define RFOR(i, b, a) for (int i = b - 1; i >= a; --i)
#define REP(i, N) FOR(i, 0, N)
#define RREP(i, N) RFOR(i, N, 0)

#define MIN(A, B) ((A) < (B) ? (A) : (B))
#define MAX(A, B) ((A) > (B) ? (A) : (B))
#define ABS(A) ((A) < 0 ? (-(A)) : (A))
#define ALL(V) V.begin(), V.end()
#define SIZE(V) (int)V.size()
#define pb push_back
#define mp make_pair
#define EPS 1e-7
#define Pi 3.14159265358979
#define FILL(a, v) memset(a, v, sizeof(a))

using namespace std;

typedef long long Long;
typedef unsigned long long ULong;
typedef unsigned int Uint;
typedef unsigned char Uchar;
typedef vector<int> VI;
typedef pair<int, int> PII;

#define X first
#define Y second

typedef std::pair<int, int> pii;
typedef long long ll;
typedef unsigned long long ull;
typedef unsigned int ui;
typedef pair<ui, ui> puu;

template <typename T, typename U>
std::istream &operator>>(std::istream &i, pair<T, U> &p) {
  i >> p.X >> p.Y;
  return i;
}
template <typename T> std::istream &operator>>(std::istream &i, vector<T> &t) {
  for (auto &v : t) {
    i >> v;
  }
  return i;
}
template <typename T, typename U>
std::ostream &operator<<(std::ostream &o, const pair<T, U> &p) {
  o << p.X << ' ' << p.Y;
  return o;
}
template <typename T>
std::ostream &operator<<(std::ostream &o, const vector<T> &t) {
  if (t.empty())
    o << '\n';
  for (size_t i = 0; i < t.size(); ++i) {
    o << t[i] << " \n"[i == t.size() - 1];
  }
  return o;
}
template <typename T> using minheap = priority_queue<T, vector<T>, greater<T>>;
template <typename T> using maxheap = priority_queue<T, vector<T>, less<T>>;
template <typename T> bool in(T a, T b, T c) { return a <= b && b < c; }
ui logceil(int x) { return 8 * sizeof(int) - __builtin_clz(x); }

namespace std {
template <typename T, typename U> struct hash<pair<T, U>> {
  hash<T> t;
  hash<U> u;
  size_t operator()(const pair<T, U> &p) const {
    return t(p.x) ^ (u(p.y) << 7);
  }
};
} // namespace std
template <typename T, typename F> T bsh(T l, T h, const F &f) {
  T r = -1, m;
  while (l <= h) {
    m = (l + h) / 2;
    if (f(m)) {
      l = m + 1;
      r = m;
    } else {
      h = m - 1;
    }
  }
  return r;
}
template <typename F>
double bshd(double l, double h, const F &f, double p = 1e-9) {
  ui r = 3 + (ui)log2((h - l) / p);
  while (r--) {
    double m = (l + h) / 2;
    if (f(m)) {
      l = m;
    } else {
      h = m;
    }
  }
  return (l + h) / 2;
}
template <typename T, typename F> T bsl(T l, T h, const F &f) {
  T r = -1, m;
  while (l <= h) {
    m = (l + h) / 2;
    if (f(m)) {
      h = m - 1;
      r = m;
    } else {
      l = m + 1;
    }
  }
  return r;
}
template <typename F>
double bsld(double l, double h, const F &f, double p = 1e-9) {
  ui r = 3 + (ui)log2((h - l) / p);
  while (r--) {
    double m = (l + h) / 2;
    if (f(m)) {
      h = m;
    } else {
      l = m;
    }
  }
  return (l + h) / 2;
}
template <typename T> T gcd(T a, T b) {
  if (a < b)
    swap(a, b);
  return b ? gcd(b, a % b) : a;
}

template <typename T> class vector2 : public vector<vector<T>> {
public:
  vector2() {}
  vector2(size_t a, size_t b, T t = T())
      : vector<vector<T>>(a, vector<T>(b, t)) {}
};
template <typename T> class vector3 : public vector<vector2<T>> {
public:
  vector3() {}
  vector3(size_t a, size_t b, size_t c, T t = T())
      : vector<vector2<T>>(a, vector2<T>(b, c, t)) {}
};
template <typename T> class vector4 : public vector<vector3<T>> {
public:
  vector4() {}
  vector4(size_t a, size_t b, size_t c, size_t d, T t = T())
      : vector<vector3<T>>(a, vector3<T>(b, c, d, t)) {}
};
template <typename T> class vector5 : public vector<vector4<T>> {
public:
  vector5() {}
  vector5(size_t a, size_t b, size_t c, size_t d, size_t e, T t = T())
      : vector<vector4<T>>(a, vector4<T>(b, c, d, e, t)) {}
};

void fastIO() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);
}

#endif

const int MAXN = 100100;

VI g[MAXN];

set<int> v;

int go(int v, int p) {
  if (g[v].size() > 2)
    return v;
  for (auto nv : g[v])
    if (nv != p)
      return go(nv, v);
}

class CThreeCircuits {
public:
  string solve1(std::istream &in) {
    fastIO();
    int n, m;
    in >> n >> m;

    v.clear();

    REP(i, n) { g[i].clear(); }

    int b, c;

    REP(i, m) {
      in >> b >> c;
      --b;
      --c;
      g[b].push_back(c);
      g[c].push_back(b);
    }

    bool bad = false;
    bool has6 = false;

    REP(i, n) {
      if (g[i].size() % 2 == 1)
        bad = true;
      if (g[i].size() >= 4) {
        v.insert(i);
      }
      if (g[i].size() >= 6)
        has6 = true;
    }

    if (bad) {
      return "No";
    }

    int c4 = v.size();

    if (has6 || c4 >= 3) {
      return "Yes";
    }

    if (c4 < 2) {
      return "No";
    }

    int c1 = *v.begin();

    for (auto v : g[c1]) {
      if (go(v, c1) == c1)
        return "Yes";
    }

    return "No";
  }

  void solve(std::istream &in, std::ostream &out) { out << solve1(in) << endl; }
};

int main() {
  CThreeCircuits solver;
  std::istream &in(std::cin);
  std::ostream &out(std::cout);
  solver.solve(in, out);
  return 0;
}