隔了好久才发了这一发loj的题解。
但是，ZJOI为什么一直有九条可怜这个名字？？？
算了，不生气。
直接看代码吧。
/* *Made by Ying Youyu. */ #include #include #include #include #include #include #include #include using namespace std; vector E[5005]; vector kind[1250]; vector T[15]; int rnd[2005]; int dp[5005][1250]; int crt[20] , ntd[1250]; int C[5005][20]; int inv[21]; const int mod = 998244353; const int inv6 = 166374059; int n , kk , ans = 0 , limit , cnt = 0; int p[20] , tot = 0 , e_tot = 0; map mp; map hashh; map , int> edge; int seed = 91478513 , a = 16554871 , b = 35659598; int power(int a,int b) { int temp = a , ans = 1; while(b){ if(b&1) ans = (1LL * ans * temp) % mod; temp = (1LL * temp * temp) % mod; b >>= 1; } return ans; } inline int rand() { return seed = (1LL * (seed ^ a) * b) % mod; } int get_hash(int fa,int u) { long long h = 1; vector hh; for(int i = 0;i < T[u].size();i++){ if(T[u][i] != fa){ int g = get_hash(u , T[u][i]); h += rnd[g]; hh.push_back(g); } } map::iterator it = hashh.find(h); if(it != hashh.end()) return it->second; hashh.insert(pair{h , ++tot}); kind[tot] = hh;ntd[tot] = 1; sort(kind[tot].begin() , kind[tot].end()); int qq = 1 , start = 0;ntd[tot] = 1; for(;start < kind[tot].size() && kind[tot][start] == 1;start++); for(int i = start + 1;i < kind[tot].size();i++){ if(kind[tot][i] == 1) continue; if(kind[tot][i] == kind[tot][i - 1]) qq++; else{ ntd[tot] = (1LL * ntd[tot] * inv[qq]) % mod; qq = 1; } } ntd[tot] = (1LL * ntd[tot] * inv[qq]) % mod; return tot; } int get_p(int fa,int u) { long long h = 1; for(int i = 0;i < T[u].size();i++){ if(T[u][i] != fa){ int g = get_p(u , T[u][i]); if(g == -1) return -1; h += rnd[g]; } } map::iterator it = hashh.find(h); if(it != hashh.end()) return it->second; return -1; } inline int get_num(int u,int v) { if(u > v) swap(u , v); map , int>::iterator it = edge.find(pair{u , v}); if(it != edge.end()) return it->second; e_tot++; edge.insert(pair,int>{pair{u , v} , e_tot}); return e_tot; } int get_node(int cnode , int k , vector G[]) { edge.clear();e_tot = 0; int q = 0; for(int i = 1;i <= cnode;i++) q += G[i].size(); q /= 2; if(k == 2){ int ans = 0; for(int i = 1;i <= cnode;i++) ans = (ans + 1LL * (G[i].size() - 1) * G[i].size()) % mod; return (1LL * ans * inv[2]); } if(k == 3){ int ans = 0; for(int i = 1;i <= cnode;i++){ for(int j = 0;j < G[i].size();j++){ if(i > G[i][j]) continue; if(G[i].size() + G[G[i][j]].size() < 4) continue; int d = G[i].size() + G[G[i][j]].size() - 2; ans = (ans + 1LL * d * (d - 1) % mod * inv[2]) % mod; } } return ans; } if(k == 4){ vector ed[cnode + 1]; int ans = 0; for(int i = 1;i <= cnode;i++){ for(int j = 0;j < G[i].size();j++){ if(i > G[i][j]) continue; int d0 = G[i].size()+G[G[i][j]].size()-2; ed[i].push_back (d0 - 1), ed[G[i][j]].push_back (d0 - 1); if (d0 > 1) ans = (ans + 1LL * d0 * (d0 - 1) % mod * (d0 - 2) % mod) % mod; } } for(int i = 1;i <= cnode;i++){ long long x = 0, y = 0; for (int j = 0; j < ed[i].size(); ++ j) if (ed[i][j]>0) x = (x + ed[i][j]) % mod, y = (y+1LL * (ed[i][j] * ed[i][j]) % mod) % mod; ans = (ans + (x * x % mod - y + mod) % mod) % mod; } return 1LL * ans * inv[2] % mod; } vector G2[q + 1]; for(int i = 1;i <= cnode;i++){ if(G[i].size() < 2) continue; int pst[G[i].size()]; for(int j = 0;j < G[i].size();j++) pst[j] = get_num(i , G[i][j]); for(int j = 0;j < G[i].size();j++){ for(int k = j + 1;k < G[i].size();k++){ G2[pst[j]].push_back(pst[k]);G2[pst[k]].push_back(pst[j]); } } } return get_node(e_tot , k - 1 , G2); } bool connect[(1<<10) + 1]; int neigh[20]; int brout(vector G[]) { for(int i = 0;i < (1<> j-1) & 1) mask |= neigh[j]; } for(int j = 1;j <= limit;j++){ if((mask >> j - 1) & 1) {connect[i | (1<> j-1) & 1) == 0) continue; if(!pp) pp = j; for(int k = 0;k < G[j].size();k++){ if((i>>G[j][k]-1) & 1) {T[j].push_back(G[j][k]);} } } ans = (ans + mp[get_hash(0 , pp)]) % mod; } return ans; } void count() { for(int i = 1;i <= limit;i++) T[i].clear(); for(int i = 2;i <= limit;i++){ T[i].push_back(p[i]);T[p[i]].push_back(i); } int h = get_hash(0 , 1); map::iterator it = mp.find(h); if(it != mp.end()) return; for(int i = 2;i <= limit;i++){ int g = get_p(0 , i); if(g == -1) continue; map::iterator it = mp.find(g); if(it != mp.end()) {mp.insert(pair{h , it->second});return;} } vector W[limit + 1]; for(int i = 1;i <= limit;i++){ for(int j = 0;j < T[i].size();j++) W[i].push_back(T[i][j]); } int t = get_node(limit , kk , T); int g = brout(W); t = (t + mod - g) % mod; mp.insert(pair{h , t}); return; } void dfs(int x) { if(x == limit){ count();return; } for(int i = 1;i <= x;i++){ p[x + 1] = i;dfs(x + 1); } return; } void find(int fa,int u) { dp[u][1] = 1; for(int i = 0;i < E[u].size();i++){ if(E[u][i] != fa) find(u , E[u][i]); } if(E[u].size() == 1 && fa != 0) return; int siz = (fa == 0) ? E[u].size() : E[u].size() - 1; int cop[siz + 1][(1<>p) & 1){ cop[g][k] = (cop[g][k] + 1LL * cop[g - 1][k ^ (1<= kind[i].size()) dp[u][i] = (1LL * cop[siz][(1<{1 , 0}); for(int i = 2;i <= kk + 1;i++){ limit = i; dfs(1); }cnt = tot; find(0 , 1); int ans = 0; for(int i = 1;i <= n;i++){ for(int j = 1;j <= cnt;j++){ ans = (ans + 1LL * dp[i][j] * mp[j]) % mod; } } printf("%d\n",ans); return 0; }
