Problem p03091 (C++)

Buggy submission (status: Runtime Error):
/*

This Submission is to determine how many 120/240 min const. delivery point there
are.

//info
120 req. steps <= 5
*/
#define _CRT_SECURE_NO_WARNINGS
#include <algorithm>
#include <bitset>
#include <cassert>
#include <cctype>
#include <complex>
#include <cstdlib>
#include <cstring>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <list>
#include <map>
#include <math.h>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <stdio.h>
#include <stdlib.h>
#include <string>
#include <time.h>
#include <typeinfo>
#include <unordered_map>
#include <utility>
#include <vector>
using namespace std;
typedef string::const_iterator State;
#define Ma_PI 3.141592653589793
#define eps 1e-5
#define LONG_INF 1e18
#define GOLD 1.61803398874989484820458
#define MAX_MOD 1000000007
#define MOD 1000000007
#define seg_size 262144
#define REP(a, b) for (long long a = 0; a < b; ++a)

unsigned long xor128() {
  static unsigned long x = time(NULL), y = 362436069, z = 521288629,
                       w = 88675123;
  unsigned long t = (x ^ (x << 11));
  x = y;
  y = z;
  z = w;
  return (w = (w ^ (w >> 19)) ^ (t ^ (t >> 8)));
}
double dot(complex<double> a, complex<double> b) {
  return a.real() * b.real() + a.imag() * b.imag();
}
double gyaku_dot(complex<double> a, complex<double> b) {
  return a.real() * b.imag() - a.imag() * b.real();
}
double leng(complex<double> a) {
  return sqrt(a.real() * a.real() + a.imag() * a.imag());
}
double angles(complex<double> a, complex<double> b) {
  double cosine = dot(a, b) / (leng(a) * leng(b));
  double sine = gyaku_dot(a, b) / (leng(a) * leng(b));
  double kaku = acos(min((double)1.0, max((double)-1.0, cosine)));
  if (sine <= 0) {
    kaku = 2 * Ma_PI - kaku;
  }
  return kaku;
}
vector<int> convex_hull(vector<complex<double>> a) {
  vector<int> ans;
  double now_minnest = a[0].real();
  int now_itr = 0;
  REP(i, a.size()) {
    if (now_minnest > a[i].real()) {
      now_minnest = a[i].real();
      now_itr = i;
    }
  }
  ans.push_back(now_itr);
  complex<double> ba(0, 1);
  while (true) {
    int now_go = 0;
    double now_min = 0;
    double now_length = 0;
    int starter = ans[ans.size() - 1];
    for (int i = 0; i < a.size(); ++i) {
      if (i != starter) {
        double goa = angles(ba, a[i] - a[starter]);
        if (goa - now_min >= eps ||
            (abs(goa - now_min) <= eps &&
             (abs(a[i] - a[starter]) - now_length) >= eps)) {
          now_min = goa;
          now_go = i;
          now_length = abs(a[i] - a[starter]);
        }
      }
    }
    if (now_go == ans[0])
      break;
    ans.push_back(now_go);
    ba = complex<double>(a[now_go] - a[starter]);
  }
  return ans;
}
vector<int> vertexs[200000];
int visited[200000];
vector<int> hoge;
int target = 0;
int dfs(int now, int back) {
  for (int q = 0; q < vertexs[now].size(); ++q) {
    if (vertexs[now][q] == back)
      continue;
    if (vertexs[now][q] == target)
      return 1;
    int bad = 0;
    REP(j, 2) {
      if (vertexs[now][q] == hoge[j]) {
        bad = 1;
        break;
      }
    }
    if (bad == 1)
      continue;
    if (visited[vertexs[now][q]] == 1)
      continue;
    visited[vertexs[now][q]] = 1;
    int now = dfs(vertexs[now][q], now);
    if (now == 1)
      return 1;
  }
  return 0;
}
int main() {
  int n, m;
  cin >> n >> m;
  REP(i, m) {
    int a, b;
    cin >> a >> b;
    vertexs[a].push_back(b);
    vertexs[b].push_back(a);
  }
  REP(i, n) {
    if (vertexs[i + 1].size() % 2 == 1) {
      cout << "No" << endl;
      return 0;
    }
  }
  REP(i, n) {
    if (vertexs[i + 1].size() >= 6) {
      cout << "Yes" << endl;
      return 0;
    }
    if (vertexs[i + 1].size() == 4) {
      hoge.push_back(i + 1);
    }
  }
  if (hoge.size() >= 3) {
    cout << "Yes" << endl;
    return 0;
  }
  if (hoge.size() <= 1) {
    cout << "No" << endl;
    return 0;
  }
  REP(q, 2) {
    target = hoge[q];
    visited[target] = 1;
    int tmp = dfs(target, -1);
    if (tmp == 0) {
      cout << "No" << endl;
      return 0;
    }
  }
  cout << "Yes" << endl;
  return 0;
}

Fixed submission:
/*

This Submission is to determine how many 120/240 min const. delivery point there
are.

//info
120 req. steps <= 5
*/
#define _CRT_SECURE_NO_WARNINGS
#include <algorithm>
#include <bitset>
#include <cassert>
#include <cctype>
#include <complex>
#include <cstdlib>
#include <cstring>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <list>
#include <map>
#include <math.h>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <stdio.h>
#include <stdlib.h>
#include <string>
#include <time.h>
#include <typeinfo>
#include <unordered_map>
#include <utility>
#include <vector>
using namespace std;
typedef string::const_iterator State;
#define Ma_PI 3.141592653589793
#define eps 1e-5
#define LONG_INF 1e18
#define GOLD 1.61803398874989484820458
#define MAX_MOD 1000000007
#define MOD 1000000007
#define seg_size 262144
#define REP(a, b) for (long long a = 0; a < b; ++a)

unsigned long xor128() {
  static unsigned long x = time(NULL), y = 362436069, z = 521288629,
                       w = 88675123;
  unsigned long t = (x ^ (x << 11));
  x = y;
  y = z;
  z = w;
  return (w = (w ^ (w >> 19)) ^ (t ^ (t >> 8)));
}
double dot(complex<double> a, complex<double> b) {
  return a.real() * b.real() + a.imag() * b.imag();
}
double gyaku_dot(complex<double> a, complex<double> b) {
  return a.real() * b.imag() - a.imag() * b.real();
}
double leng(complex<double> a) {
  return sqrt(a.real() * a.real() + a.imag() * a.imag());
}
double angles(complex<double> a, complex<double> b) {
  double cosine = dot(a, b) / (leng(a) * leng(b));
  double sine = gyaku_dot(a, b) / (leng(a) * leng(b));
  double kaku = acos(min((double)1.0, max((double)-1.0, cosine)));
  if (sine <= 0) {
    kaku = 2 * Ma_PI - kaku;
  }
  return kaku;
}
vector<int> convex_hull(vector<complex<double>> a) {
  vector<int> ans;
  double now_minnest = a[0].real();
  int now_itr = 0;
  REP(i, a.size()) {
    if (now_minnest > a[i].real()) {
      now_minnest = a[i].real();
      now_itr = i;
    }
  }
  ans.push_back(now_itr);
  complex<double> ba(0, 1);
  while (true) {
    int now_go = 0;
    double now_min = 0;
    double now_length = 0;
    int starter = ans[ans.size() - 1];
    for (int i = 0; i < a.size(); ++i) {
      if (i != starter) {
        double goa = angles(ba, a[i] - a[starter]);
        if (goa - now_min >= eps ||
            (abs(goa - now_min) <= eps &&
             (abs(a[i] - a[starter]) - now_length) >= eps)) {
          now_min = goa;
          now_go = i;
          now_length = abs(a[i] - a[starter]);
        }
      }
    }
    if (now_go == ans[0])
      break;
    ans.push_back(now_go);
    ba = complex<double>(a[now_go] - a[starter]);
  }
  return ans;
}
vector<int> vertexs[200000];
int visited[200000];
vector<int> hoge;
int target = 0;
int dfs(int now, int back) {
  for (int q = 0; q < vertexs[now].size(); ++q) {
    if (vertexs[now][q] == back)
      continue;
    if (vertexs[now][q] == target)
      return 1;
    int bad = 0;
    REP(j, 2) {
      if (vertexs[now][q] == hoge[j]) {
        bad = 1;
        break;
      }
    }
    if (bad == 1)
      continue;
    if (visited[vertexs[now][q]] == 1)
      continue;
    visited[vertexs[now][q]] = 1;
    int nowa = dfs(vertexs[now][q], now);
    if (nowa == 1)
      return 1;
  }
  return 0;
}
int main() {
  int n, m;
  cin >> n >> m;
  REP(i, m) {
    int a, b;
    cin >> a >> b;
    vertexs[a].push_back(b);
    vertexs[b].push_back(a);
  }
  REP(i, n) {
    if (vertexs[i + 1].size() % 2 == 1) {
      cout << "No" << endl;
      return 0;
    }
  }
  REP(i, n) {
    if (vertexs[i + 1].size() >= 6) {
      cout << "Yes" << endl;
      return 0;
    }
    if (vertexs[i + 1].size() == 4) {
      hoge.push_back(i + 1);
    }
  }
  if (hoge.size() >= 3) {
    cout << "Yes" << endl;
    return 0;
  }
  if (hoge.size() <= 1) {
    cout << "No" << endl;
    return 0;
  }
  REP(q, 2) {
    target = hoge[q];
    visited[target] = 1;
    int tmp = dfs(target, -1);
    if (tmp == 0) {
      cout << "No" << endl;
      return 0;
    }
  }
  cout << "Yes" << endl;
  return 0;
}