Problem p03052 (C++)

Buggy submission (status: Time Limit Exceeded):
#pragma GCC target("avx")            // CPU 処理並列化
#pragma GCC optimize("O3")           // CPU 処理並列化
#pragma GCC optimize("unroll-loops") // 条件処理の呼び出しを減らす
// #define BEGIN_STACK_EXTEND(size) void * stack_extend_memory_ =
// malloc(size);void * stack_extend_origin_memory_;char *
// stack_extend_dummy_memory_ = (char*)alloca((1+(int)(((long
// long)stack_extend_memory_)&127))*16);*stack_extend_dummy_memory_ = 0;asm
// volatile("mov %%rsp, %%rbx\nmov %%rax,
// %%rsp":"=b"(stack_extend_origin_memory_):"a"((char*)stack_extend_memory_+(size)-1024));
// #define END_STACK_EXTEND asm volatile("mov %%rax,
// %%rsp"::"a"(stack_extend_origin_memory_));free(stack_extend_memory_);

#include <algorithm>
#include <bitset>
#include <cassert>
#include <complex>
#include <deque>
#include <map>
#include <math.h>
#include <numeric>
#include <queue>
#include <set>
#include <stack>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <string>
#include <time.h>
#include <unordered_map>
#include <unordered_set>
#include <vector>
using namespace std;
const long long mod = 1000000007;
const long long inf = mod * mod;
const long long d2 = (mod + 1) / 2;
const long double EPS = 1e-9;
const long double INF = 1e+10;
const long double PI = acos(-1.0);
const int C_SIZE = 3100000;
const int UF_SIZE = 3100000;
namespace {
long long fact[C_SIZE];
long long finv[C_SIZE];
long long inv[C_SIZE];
inline long long Comb(int a, int b) {
  if (a < b || b < 0)
    return 0;
  return fact[a] * finv[b] % mod * finv[a - b] % mod;
}
void init_C(int n) {
  fact[0] = finv[0] = inv[1] = 1;
  for (int i = 2; i < n; i++) {
    inv[i] = (mod - (mod / i) * inv[mod % i] % mod) % mod;
  }
  for (int i = 1; i < n; i++) {
    fact[i] = fact[i - 1] * i % mod;
    finv[i] = finv[i - 1] * inv[i] % mod;
  }
}
long long pw(long long a, long long b) {
  if (a < 0LL)
    return 0;
  if (b < 0LL)
    return 0;
  long long ret = 1;
  while (b) {
    if (b % 2)
      ret = ret * a % mod;
    a = a * a % mod;
    b /= 2;
  }
  return ret;
}
long long pw_mod(long long a, long long b, long long M) {
  if (a < 0LL)
    return 0;
  if (b < 0LL)
    return 0;
  long long ret = 1;
  while (b) {
    if (b % 2)
      ret = ret * a % M;
    a = a * a % M;
    b /= 2;
  }
  return ret;
}
int pw_mod_int(int a, int b, int M) {
  if (a < 0)
    return 0;
  if (b < 0)
    return 0;
  int ret = 1;
  while (b) {
    if (b % 2)
      ret = (long long)ret * a % M;
    a = (long long)a * a % M;
    b /= 2;
  }
  return ret;
}
int ABS(int a) { return max(a, -a); }
long long ABS(long long a) { return max(a, -a); }
double ABS(double a) { return max(a, -a); }
int sig(double r) { return (r < -EPS) ? -1 : (r > +EPS) ? +1 : 0; }
int UF[UF_SIZE];
void init_UF(int n) {
  for (int i = 0; i < n; i++)
    UF[i] = -1;
}
int FIND(int a) {
  if (UF[a] < 0)
    return a;
  return UF[a] = FIND(UF[a]);
}
void UNION(int a, int b) {
  a = FIND(a);
  b = FIND(b);
  if (a == b)
    return;
  if (UF[a] > UF[b])
    swap(a, b);
  UF[a] += UF[b];
  UF[b] = a;
}
} // namespace
// ここから編集しろ
int L[310];
int R[310];
pair<long long, long long> dp[2][1 << 19];
int K[1 << 19];
int TMP[310];
vector<int> to[1 << 19];
int main() {
  int a, b;
  scanf("%d%d", &a, &b);
  for (int i = 0; i < b; i++) {
    scanf("%d%d", L + i, R + i);
    L[i]--;
    R[i]--;
  }
  int n = a - 1;
  for (int i = 0; i < (1 << n); i++) {
    init_UF(a);
    for (int j = 0; j < n; j++) {
      if (i & (1 << j)) {
        UNION(L[j], R[j]);
        K[i]++;
      } else
        to[i].push_back(1 << j);
    }
    for (int j = 0; j < a; j++)
      TMP[j] = FIND(j);
    for (int j = n; j < b; j++) {
      if (TMP[L[j]] == TMP[R[j]])
        K[i]++;
    }
  }

  dp[0][0].first = 1;
  for (int i = 0; i < b; i++) {
    int h = i % 2;
    int g = !h;
    for (int j = 0; j < (1 << n); j++)
      dp[g][j] = make_pair(0LL, 0LL);
    for (int j = (1 << n) - 1; j >= 0; j--) {
      if (!dp[h][j].first && !dp[h][j].second) {
        continue;
      }
      if (K[j] > i) {
        dp[g][j].first += dp[h][j].first * (K[j] - i);
        dp[g][j].second += dp[h][j].second * (K[j] - i);
      }
      long long ad = dp[h][j].second + dp[h][j].first * (i + 1);
      for (int k = 0; k < to[j].size(); k++) {
        dp[g][j | to[j][k]].first += dp[h][j].first;
        dp[g][j | to[j][k]].second += ad;
      }
    }
    for (int j = 0; j < (1 << n); j++) {
      dp[g][j].first %= mod;
      dp[g][j].second %= mod;
    }
  }
  printf("%lld\n", dp[b % 2][(1 << n) - 1].second % mod);
}

Fixed submission:
#pragma GCC target("avx")            // CPU 処理並列化
#pragma GCC optimize("O3")           // CPU 処理並列化
#pragma GCC optimize("unroll-loops") // 条件処理の呼び出しを減らす
// #define BEGIN_STACK_EXTEND(size) void * stack_extend_memory_ =
// malloc(size);void * stack_extend_origin_memory_;char *
// stack_extend_dummy_memory_ = (char*)alloca((1+(int)(((long
// long)stack_extend_memory_)&127))*16);*stack_extend_dummy_memory_ = 0;asm
// volatile("mov %%rsp, %%rbx\nmov %%rax,
// %%rsp":"=b"(stack_extend_origin_memory_):"a"((char*)stack_extend_memory_+(size)-1024));
// #define END_STACK_EXTEND asm volatile("mov %%rax,
// %%rsp"::"a"(stack_extend_origin_memory_));free(stack_extend_memory_);

#include <algorithm>
#include <bitset>
#include <cassert>
#include <complex>
#include <deque>
#include <map>
#include <math.h>
#include <numeric>
#include <queue>
#include <set>
#include <stack>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <string>
#include <time.h>
#include <unordered_map>
#include <unordered_set>
#include <vector>
using namespace std;
const long long mod = 1000000007;
const long long inf = mod * mod;
const long long d2 = (mod + 1) / 2;
const long double EPS = 1e-9;
const long double INF = 1e+10;
const long double PI = acos(-1.0);
const int C_SIZE = 3100000;
const int UF_SIZE = 3100000;
namespace {
long long fact[C_SIZE];
long long finv[C_SIZE];
long long inv[C_SIZE];
inline long long Comb(int a, int b) {
  if (a < b || b < 0)
    return 0;
  return fact[a] * finv[b] % mod * finv[a - b] % mod;
}
void init_C(int n) {
  fact[0] = finv[0] = inv[1] = 1;
  for (int i = 2; i < n; i++) {
    inv[i] = (mod - (mod / i) * inv[mod % i] % mod) % mod;
  }
  for (int i = 1; i < n; i++) {
    fact[i] = fact[i - 1] * i % mod;
    finv[i] = finv[i - 1] * inv[i] % mod;
  }
}
long long pw(long long a, long long b) {
  if (a < 0LL)
    return 0;
  if (b < 0LL)
    return 0;
  long long ret = 1;
  while (b) {
    if (b % 2)
      ret = ret * a % mod;
    a = a * a % mod;
    b /= 2;
  }
  return ret;
}
long long pw_mod(long long a, long long b, long long M) {
  if (a < 0LL)
    return 0;
  if (b < 0LL)
    return 0;
  long long ret = 1;
  while (b) {
    if (b % 2)
      ret = ret * a % M;
    a = a * a % M;
    b /= 2;
  }
  return ret;
}
int pw_mod_int(int a, int b, int M) {
  if (a < 0)
    return 0;
  if (b < 0)
    return 0;
  int ret = 1;
  while (b) {
    if (b % 2)
      ret = (long long)ret * a % M;
    a = (long long)a * a % M;
    b /= 2;
  }
  return ret;
}
int ABS(int a) { return max(a, -a); }
long long ABS(long long a) { return max(a, -a); }
double ABS(double a) { return max(a, -a); }
int sig(double r) { return (r < -EPS) ? -1 : (r > +EPS) ? +1 : 0; }
int UF[UF_SIZE];
void init_UF(int n) {
  for (int i = 0; i < n; i++)
    UF[i] = -1;
}
int FIND(int a) {
  if (UF[a] < 0)
    return a;
  return UF[a] = FIND(UF[a]);
}
void UNION(int a, int b) {
  a = FIND(a);
  b = FIND(b);
  if (a == b)
    return;
  if (UF[a] > UF[b])
    swap(a, b);
  UF[a] += UF[b];
  UF[b] = a;
}
} // namespace
// ここから編集しろ
int L[310];
int R[310];
pair<long long, long long> dp[2][1 << 19];
int K[1 << 19];
int TMP[310];
vector<int> to[1 << 19];
int main() {
  int a, b;
  scanf("%d%d", &a, &b);
  for (int i = 0; i < b; i++) {
    scanf("%d%d", L + i, R + i);
    L[i]--;
    R[i]--;
  }
  int n = a - 1;
  for (int i = 0; i < (1 << n); i++) {
    init_UF(a);
    for (int j = 0; j < n; j++) {
      if (i & (1 << j)) {
        UNION(L[j], R[j]);
        K[i]++;
      } else
        to[i].push_back(1 << j);
    }
    for (int j = 0; j < a; j++)
      TMP[j] = FIND(j);
    for (int j = n; j < b; j++) {
      if (TMP[L[j]] == TMP[R[j]])
        K[i]++;
    }
  }

  dp[0][0].first = 1;
  for (int i = 0; i < b; i++) {
    int h = i % 2;
    int g = !h;
    for (int j = 0; j < (1 << n); j++)
      dp[g][j] = make_pair(0LL, 0LL);
    for (int j = (1 << n) - 1; j >= 0; j--) {
      if (!dp[h][j].first && !dp[h][j].second) {
        continue;
      }
      if (K[j] > i) {
        dp[g][j].first += dp[h][j].first * (K[j] - i);
        dp[g][j].second += dp[h][j].second * (K[j] - i);
      }
      long long ad = dp[h][j].second + dp[h][j].first * (i + 1);
      for (int k = 0; k < to[j].size(); k++) {
        dp[g][j | to[j][k]].first += dp[h][j].first;
        dp[g][j | to[j][k]].second += ad;
      }
    }
    for (int j = 0; j < (1 << n); j++) {
      if (dp[g][j].first >= mod)
        dp[g][j].first %= mod;
      if (dp[g][j].second >= mod)
        dp[g][j].second %= mod;
    }
  }
  printf("%lld\n", dp[b % 2][(1 << n) - 1].second % mod);
}