Submission #2070720

---

Source Code Expand

#include <bits/stdc++.h>
using namespace std;
#define _MACRO(_1, _2, _3, NAME, ...) NAME
#define _repl(i,a,b) for(int i=(int)(a);i<(int)(b);i++)
#define _rep(i,n) _repl(i,0,n)
#define rep(...) _MACRO(__VA_ARGS__, _repl, _rep)(__VA_ARGS__)
#define mp make_pair
#define pb push_back
#define all(x) begin(x),end(x)
#define uniq(x) sort(all(x)),(x).erase(unique(all(x)),end(x))
#define fi first
#define se second
#define dbg(...) _dbg(#__VA_ARGS__, __VA_ARGS__)
void _dbg(string){cerr<<endl;}
template<class H,class... T> void _dbg(string s,H h,T... t){int l=s.find(',');cerr<<s.substr(0,l)<<" = "<<h<<", ";_dbg(s.substr(l+1),t...);}
template<class T,class U> ostream& operator<<(ostream &o, const pair<T,U> &p){o<<"("<<p.fi<<","<<p.se<<")";return o;}
template<class T> ostream& operator<<(ostream &o, const vector<T> &v){o<<"[";for(T t:v){o<<t<<",";}o<<"]";return o;}

#define INF 1120000000

template<int mod=1000000007>
class ModInt {
  int x;
public:
  ModInt() : x(0){}
  ModInt(int64_t y){ x = y % mod; if(x < 0) x += mod; }
  ModInt &operator += (const ModInt &p){ x += p.x; if(x >= mod) x -= mod; return *this; }
  ModInt &operator -= (const ModInt &p){ x -= p.x; if(x < 0) x += mod; return *this; }
  ModInt &operator *= (const ModInt &p){ x = (int) (1LL * x * p.x % mod); return *this; }
  ModInt &operator /= (const ModInt &p){ *this *= p.inverse(); return *this; }
  ModInt &operator += (const int64_t y){ x = (x + y)%mod; if(x < 0) x += mod; return *this; }
  ModInt &operator -= (const int64_t y){ x = (x - y)%mod; if(x < 0) x += mod; return *this; }
  ModInt &operator *= (const int64_t y){ x = (int) (x * y % mod); return *this; }
  ModInt &operator /= (const int64_t y){ *this *= ModInt(y).inverse(); return *this; }
  ModInt operator -() const { return ModInt(-x); }
  ModInt operator + (const ModInt &p) const { return ModInt(*this) += p; }
  ModInt operator - (const ModInt &p) const { return ModInt(*this) -= p; }
  ModInt operator * (const ModInt &p) const { return ModInt(*this) *= p; }
  ModInt operator / (const ModInt &p) const { return ModInt(*this) /= p; }
  bool operator == (const ModInt &p) const { return x == p.x; }
  bool operator != (const ModInt &p) const { return x != p.x; }
  ModInt operator + (const int64_t y) const { return ModInt(*this) += y; }
  ModInt operator - (const int64_t y) const { return ModInt(*this) -= y; }
  ModInt operator * (const int64_t y) const { return ModInt(*this) *= y; }
  ModInt operator / (const int64_t y) const { return ModInt(*this) /= y; }
  bool operator == (const int64_t y) const { return x == (mod + y%mod)%mod; }
  bool operator != (const int64_t y) const { return x != (mod + y%mod)%mod; }
  ModInt operator = (const int64_t y) { return *this = ModInt(y); }
  ModInt inverse() const {
    int a = x, b = mod, u = 1, v = 0, t;
    while(b > 0){
      t = a/b; a -= t*b; swap(a, b);
      u -= t*v; swap(u, v);
    }
    return ModInt(u);
  }
  friend ostream &operator << (ostream &os, const ModInt<mod> &p) { return os<<p.x; }
  friend istream &operator >> (istream &is, ModInt<mod> &a) { int64_t x; is>>x; a = ModInt<mod>(x); return is; }
};
using Int = ModInt<>;

Int tbl[305][305][155];
Int fact[400];
Int finv[400];

int main(){
  fact[0] = 1;
  rep(i,305) fact[i+1] = fact[i]*(i+1);
  rep(i,305) finv[i] = fact[i].inverse();

  int n,x,y,z;
  cin>>n>>x>>y>>z;

  if(x+y+z < n){
    cout << 0 << endl;
    return 0;
  }

  rep(c1,301) rep(c2,301) rep(c3,151){
    Int &v = tbl[c1][c2][c3];
    if(c1+c2<=c3) v = finv[c1] * finv[c2] * finv[c3-c1-c2];
    else v = 0;
    if(c1>0) v += tbl[c1-1][c2][c3];
    if(c2>0) v += tbl[c1][c2-1][c3];
    if(c1>0 && c2>0) v -= tbl[c1-1][c2-1][c3];
  }

  Int ans = 0;
  rep(i,x+1) rep(j,y+1) rep(k,z+1){
    for(int l=0; i+j+k+l<=n && i+j+l<=x+y; l++){
      int c1 = y+z-j-k;
      int c2 = x+z-i-k;
      int c3 = n-i-j-k-l;
      auto sel = fact[n] * finv[i] * finv[j] * finv[k] * finv[l];
      ans += sel * tbl[c1][c2][c3];
    }
  }

  cout << ans << endl;

  return 0;
}

Submission Info

Judge Result