Submission #2663590

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Source Code Expand

#include <bits/stdc++.h>
#define GET_MACRO(_1,_2,_3,_4,_5,_6,NAME,...) NAME
#define pr(...) cerr<< GET_MACRO(__VA_ARGS__,pr6,pr5,pr4,pr3,pr2,pr1)(__VA_ARGS__) <<endl
#define pr1(a) (#a)<<"="<<(a)<<" "
#define pr2(a,b) pr1(a)<<pr1(b)
#define pr3(a,b,c) pr1(a)<<pr2(b,c)
#define pr4(a,b,c,d) pr1(a)<<pr3(b,c,d)
#define pr5(a,b,c,d,e) pr1(a)<<pr4(b,c,d,e)
#define pr6(a,b,c,d,e,f) pr1(a)<<pr5(b,c,d,e,f)
#define pr7(a,b,c,d,e,f,g) pr1(a)<<pr6(b,c,d,e,f,g)
#define pr8(a,b,c,d,e,f,g,h) pr1(a)<<pr7(b,c,d,e,f,g,h)
using namespace std;
using Int = long long;
using ll = long long;
using Double = long double;
const Int INF = (1LL<<55)+1e9; // ~ 3.6 * 1e16
const Int mod = (1e9)+7;
const Double EPS = 1e-8;
const Double PI = 6.0 * asin((Double)0.5);
using P = pair<Int,Int>;
using T = tuple<Int,Int,Int>;
template<class T> T Max(T &a,T b){return a=max(a,b);}
template<class T> T Min(T &a,T b){return a=min(a,b);}
ostream& operator<<(ostream& o,P p){return o<<"("<<p.first<<","<<p.second<<")";}
ostream& operator<<(ostream& o,T t){return o<<"("<<get<0>(t)<<","<<get<1>(t)<<","<<get<2>(t)<<")";}
istream& operator>>(istream& i,P &p){return i>>p.first>>p.second;}
ostream& operator<<(ostream& o,vector<auto> &a){Int i=0;for(auto t:a)o<<(i++?" ":"")<<t;return o;}
istream& operator>>(istream& i,vector<auto> &a){for(auto &t:a)i>>t;return i;}
void prArr(auto a,string s=" "){Int i=0;for(auto t:a)cout<<(i++?s:"")<<t;cout<<endl;}
const Int N = 310;

Int n, m;
int mem[N][N][N];
bool used[N][N][N];

Int dfs(Int pos, Int num, Int cnt){

  if(pos == n-1 && num == n-1 && cnt == m) return 1;
  if(pos == n || cnt == m) return 0;
  if(used[pos][num][cnt]) return mem[pos][num][cnt];
  used[pos][num][cnt] = 1;
  
  // つなぐ
  Int a = dfs(pos, pos, cnt+1) * (num+1);
  
  // ループ
  Int b = dfs(pos, num, cnt + 1) * (pos - num);
  
  // 進む
  Int c = dfs(pos + 1, num, cnt + 1);
  
  Int res = (a + b + c) % mod;
  
  return mem[pos][num][cnt] = res;
}


signed main(){
  cin.tie(0);
  ios_base::sync_with_stdio(0);
  cout << fixed << setprecision(12);
  
  cin>>n>>m;

  Int k = 1;
  for(Int i = n-1;i>=1;i--) k = k * i % mod;

  Int ans = dfs(0, 0, 0) * k % mod;
  cout<<ans<<endl;
  
  return 0;
}

Submission Info

Judge Result