Problem p02974 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>

//    #include <boost/multiprecision/cpp_int.hpp>
#define int long long
#define inf 1000000007
#define pa pair<int, int>
#define ll long long
#define pal pair<double, double>
#define ppap pair<pa, int>
#define PI 3.14159265358979323846
#define paa pair<int, char>
#define mp make_pair
#define pb push_back
#define EPS (1e-10)

int dx[8] = {0, 1, 0, -1, 1, 1, -1, -1};
int dy[8] = {1, 0, -1, 0, -1, 1, 1, -1};
using namespace std;
class pa3 {
public:
  int x;
  int y, z;
  pa3(int x = 0, int y = 0, int z = 0) : x(x), y(y), z(z) {}
  bool operator<(const pa3 &p) const {
    if (x != p.x)
      return x < p.x;
    if (y != p.y)
      return y < p.y;
    return z < p.z;
    // return x != p.x ? x<p.x: y<p.y;
  }
  bool operator>(const pa3 &p) const {
    if (x != p.x)
      return x > p.x;
    if (y != p.y)
      return y > p.y;
    return z > p.z;
    // return x != p.x ? x<p.x: y<p.y;
  }
  bool operator==(const pa3 &p) const {
    return x == p.x && y == p.y && z == p.z;
  }
  bool operator!=(const pa3 &p) const {
    return !(x == p.x && y == p.y && z == p.z);
  }
};

class pa4 {
public:
  int x;
  int y, z, w;
  pa4(int x = 0, int y = 0, int z = 0, int w = 0) : x(x), y(y), z(z), w(w) {}
  bool operator<(const pa4 &p) const {
    if (x != p.x)
      return x < p.x;
    if (y != p.y)
      return y < p.y;
    if (z != p.z)
      return z < p.z;
    return w < p.w;
    // return x != p.x ? x<p.x: y<p.y;
  }
  bool operator>(const pa4 &p) const {
    if (x != p.x)
      return x > p.x;
    if (y != p.y)
      return y > p.y;
    if (z != p.z)
      return z > p.z;
    return w > p.w;
    // return x != p.x ? x<p.x: y<p.y;
  }
  bool operator==(const pa4 &p) const {
    return x == p.x && y == p.y && z == p.z && w == p.w;
  }
};
class pa2 {
public:
  int x, y;
  pa2(int x = 0, int y = 0) : x(x), y(y) {}
  pa2 operator+(pa2 p) { return pa2(x + p.x, y + p.y); }
  pa2 operator-(pa2 p) { return pa2(x - p.x, y - p.y); }
  bool operator<(const pa2 &p) const { return y != p.y ? y < p.y : x < p.x; }
  bool operator>(const pa2 &p) const { return x != p.x ? x < p.x : y < p.y; }
  bool operator==(const pa2 &p) const {
    return abs(x - p.x) == 0 && abs(y - p.y) == 0;
  }
  bool operator!=(const pa2 &p) const {
    return !(abs(x - p.x) == 0 && abs(y - p.y) == 0);
  }
};

string itos(int i) {
  ostringstream s;
  s << i;
  return s.str();
}

int gcd(int v, int b) {
  if (v > b)
    return gcd(b, v);
  if (v == b)
    return b;
  if (b % v == 0)
    return v;
  return gcd(v, b % v);
}

int mod;
int extgcd(int a, int b, int &x, int &y) {
  if (b == 0) {
    x = 1;
    y = 0;
    return a;
  }
  int d = extgcd(b, a % b, y, x);
  y -= a / b * x;
  return d;
}
pa operator+(const pa &l, const pa &r) {
  return {l.first + r.first, l.second + r.second};
}
pa operator-(const pa &l, const pa &r) {
  return {l.first - r.first, l.second - r.second};
}

int pr[200010];
int inv[200010];

int beki(int wa, int rr, int warukazu) {
  if (rr == 0)
    return 1 % warukazu;
  if (rr == 1)
    return wa % warukazu;
  wa %= warukazu;
  if (rr % 2 == 1)
    return ((ll)beki(wa, rr - 1, warukazu) * (ll)wa) % warukazu;
  ll zx = beki(wa, rr / 2, warukazu);
  return (zx * zx) % warukazu;
}

int comb(int nn, int rr) {
  if (rr < 0 || rr > nn || nn < 0)
    return 0;
  int r = pr[nn] * inv[rr];
  r %= mod;
  r *= inv[nn - rr];
  r %= mod;
  return r;
}

void gya(int ert) {
  pr[0] = 1;
  for (int i = 1; i <= ert; i++) {
    pr[i] = (pr[i - 1] * i) % mod;
  }
  inv[ert] = beki(pr[ert], mod - 2, mod);
  for (int i = ert - 1; i >= 0; i--) {
    inv[i] = inv[i + 1] * (i + 1) % mod;
  }
}

//   cin.tie(0);
//	ios::sync_with_stdio(false);
// priority_queue<pa3,vector<pa3>,greater<pa3>> pq;
// sort(ve.begin(),ve.end(),greater<int>());
//    mt19937(clock_per_sec);
//  mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count()) ;

//----------------kokomade tenpure------------

int dp[60][60][2600] = {};
signed main() {

  cin.tie(0);
  ios::sync_with_stdio(false);

  dp[0][0][0] = 1;
  int n, k;
  cin >> n >> k;
  for (int i = 1; i <= n; i++)
    for (int j = 0; j <= i; j++)
      for (int h = 0; h <= n * n; h++) {
        /*
        dp[i+1][j][h+2*(i+1-j)]+= dp[i][j][h]*(i+1-j)%inf;
        dp[i+1][j+1][h+] += dp[i][j][h]*
        */
        if (j >= 0 && h - 2 * (i - 1 - j + 1) >= 0)
          dp[i][j][h] += dp[i - 1][j - 1][h - 2 * (i - 1 - j + 1)];
        // if(i==2&& j==2 && h==0) cout<<dp[i][j][h]<<endl;
        if (j - 2 >= 0 && h - 2 * (i - 1 - j + 2) >= 0)
          dp[i][j][h] += dp[i - 1][j - 2][h - 2 * (i - 1 - j + 2)] *
                         (i - 1 - j + 2) * (i - 1 - j + 2) % inf;
        if (j - 1 >= 0 && h - 2 * (i - 1 - j + 1) >= 0)
          dp[i][j][h] +=
              dp[i - 1][j - 1][h - 2 * (i - 1 - j + 1)] * (i - 1 - j + 1) % inf;
        if (j - 1 >= 0 && h - 2 * (i - 1 - j + 1) >= 0)
          dp[i][j][h] +=
              dp[i - 1][j - 1][h - 2 * (i - 1 - j + 1)] * (i - 1 - j + 1) % inf;
        if (j >= 0 && h - 2 * (i - 1 - j) >= 0)
          dp[i][j][h] += dp[i - 1][j][h - 2 * (i - 1 - j)] % inf;
        // cout<<i<<" "<<j<<" "<<h<<" "<<dp[i][j][h]<<endl;
        dp[i][j][h] %= inf;
      }

  cout << dp[n][n][k] << endl;
  return 0;
}


Fixed submission:
#include <bits/stdc++.h>

//    #include <boost/multiprecision/cpp_int.hpp>
#define int long long
#define inf 1000000007
#define pa pair<int, int>
#define ll long long
#define pal pair<double, double>
#define ppap pair<pa, int>
#define PI 3.14159265358979323846
#define paa pair<int, char>
#define mp make_pair
#define pb push_back
#define EPS (1e-10)

int dx[8] = {0, 1, 0, -1, 1, 1, -1, -1};
int dy[8] = {1, 0, -1, 0, -1, 1, 1, -1};
using namespace std;
class pa3 {
public:
  int x;
  int y, z;
  pa3(int x = 0, int y = 0, int z = 0) : x(x), y(y), z(z) {}
  bool operator<(const pa3 &p) const {
    if (x != p.x)
      return x < p.x;
    if (y != p.y)
      return y < p.y;
    return z < p.z;
    // return x != p.x ? x<p.x: y<p.y;
  }
  bool operator>(const pa3 &p) const {
    if (x != p.x)
      return x > p.x;
    if (y != p.y)
      return y > p.y;
    return z > p.z;
    // return x != p.x ? x<p.x: y<p.y;
  }
  bool operator==(const pa3 &p) const {
    return x == p.x && y == p.y && z == p.z;
  }
  bool operator!=(const pa3 &p) const {
    return !(x == p.x && y == p.y && z == p.z);
  }
};

class pa4 {
public:
  int x;
  int y, z, w;
  pa4(int x = 0, int y = 0, int z = 0, int w = 0) : x(x), y(y), z(z), w(w) {}
  bool operator<(const pa4 &p) const {
    if (x != p.x)
      return x < p.x;
    if (y != p.y)
      return y < p.y;
    if (z != p.z)
      return z < p.z;
    return w < p.w;
    // return x != p.x ? x<p.x: y<p.y;
  }
  bool operator>(const pa4 &p) const {
    if (x != p.x)
      return x > p.x;
    if (y != p.y)
      return y > p.y;
    if (z != p.z)
      return z > p.z;
    return w > p.w;
    // return x != p.x ? x<p.x: y<p.y;
  }
  bool operator==(const pa4 &p) const {
    return x == p.x && y == p.y && z == p.z && w == p.w;
  }
};
class pa2 {
public:
  int x, y;
  pa2(int x = 0, int y = 0) : x(x), y(y) {}
  pa2 operator+(pa2 p) { return pa2(x + p.x, y + p.y); }
  pa2 operator-(pa2 p) { return pa2(x - p.x, y - p.y); }
  bool operator<(const pa2 &p) const { return y != p.y ? y < p.y : x < p.x; }
  bool operator>(const pa2 &p) const { return x != p.x ? x < p.x : y < p.y; }
  bool operator==(const pa2 &p) const {
    return abs(x - p.x) == 0 && abs(y - p.y) == 0;
  }
  bool operator!=(const pa2 &p) const {
    return !(abs(x - p.x) == 0 && abs(y - p.y) == 0);
  }
};

string itos(int i) {
  ostringstream s;
  s << i;
  return s.str();
}

int gcd(int v, int b) {
  if (v > b)
    return gcd(b, v);
  if (v == b)
    return b;
  if (b % v == 0)
    return v;
  return gcd(v, b % v);
}

int mod;
int extgcd(int a, int b, int &x, int &y) {
  if (b == 0) {
    x = 1;
    y = 0;
    return a;
  }
  int d = extgcd(b, a % b, y, x);
  y -= a / b * x;
  return d;
}
pa operator+(const pa &l, const pa &r) {
  return {l.first + r.first, l.second + r.second};
}
pa operator-(const pa &l, const pa &r) {
  return {l.first - r.first, l.second - r.second};
}

int pr[200010];
int inv[200010];

int beki(int wa, int rr, int warukazu) {
  if (rr == 0)
    return 1 % warukazu;
  if (rr == 1)
    return wa % warukazu;
  wa %= warukazu;
  if (rr % 2 == 1)
    return ((ll)beki(wa, rr - 1, warukazu) * (ll)wa) % warukazu;
  ll zx = beki(wa, rr / 2, warukazu);
  return (zx * zx) % warukazu;
}

int comb(int nn, int rr) {
  if (rr < 0 || rr > nn || nn < 0)
    return 0;
  int r = pr[nn] * inv[rr];
  r %= mod;
  r *= inv[nn - rr];
  r %= mod;
  return r;
}

void gya(int ert) {
  pr[0] = 1;
  for (int i = 1; i <= ert; i++) {
    pr[i] = (pr[i - 1] * i) % mod;
  }
  inv[ert] = beki(pr[ert], mod - 2, mod);
  for (int i = ert - 1; i >= 0; i--) {
    inv[i] = inv[i + 1] * (i + 1) % mod;
  }
}

//   cin.tie(0);
//	ios::sync_with_stdio(false);
// priority_queue<pa3,vector<pa3>,greater<pa3>> pq;
// sort(ve.begin(),ve.end(),greater<int>());
//    mt19937(clock_per_sec);
//  mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count()) ;

//----------------kokomade tenpure------------

int dp[60][60][2600] = {};
signed main() {

  cin.tie(0);
  ios::sync_with_stdio(false);

  dp[0][0][0] = 1;
  int n, k;
  cin >> n >> k;
  for (int i = 1; i <= n; i++)
    for (int j = 0; j <= i; j++)
      for (int h = 0; h <= n * n; h++) {
        /*
        dp[i+1][j][h+2*(i+1-j)]+= dp[i][j][h]*(i+1-j)%inf;
        dp[i+1][j+1][h+] += dp[i][j][h]*
        */
        if (j - 1 >= 0 && h - 2 * (i - 1 - j + 1) >= 0)
          dp[i][j][h] += dp[i - 1][j - 1][h - 2 * (i - 1 - j + 1)];
        // if(i==2&& j==2 && h==0) cout<<dp[i][j][h]<<endl;
        if (j - 2 >= 0 && h - 2 * (i - 1 - j + 2) >= 0)
          dp[i][j][h] += dp[i - 1][j - 2][h - 2 * (i - 1 - j + 2)] *
                         (i - 1 - j + 2) * (i - 1 - j + 2) % inf;
        if (j - 1 >= 0 && h - 2 * (i - 1 - j + 1) >= 0)
          dp[i][j][h] +=
              dp[i - 1][j - 1][h - 2 * (i - 1 - j + 1)] * (i - 1 - j + 1) % inf;
        if (j - 1 >= 0 && h - 2 * (i - 1 - j + 1) >= 0)
          dp[i][j][h] +=
              dp[i - 1][j - 1][h - 2 * (i - 1 - j + 1)] * (i - 1 - j + 1) % inf;
        if (j >= 0 && h - 2 * (i - 1 - j) >= 0)
          dp[i][j][h] += dp[i - 1][j][h - 2 * (i - 1 - j)] % inf;
        // cout<<i<<" "<<j<<" "<<h<<" "<<dp[i][j][h]<<endl;
        dp[i][j][h] %= inf;
      }

  cout << dp[n][n][k] << endl;
  return 0;
}