在合并的时候有可以加等于，或者继续用小于，
比如siz[x]和siz[y]合并，小于的区间为max(siz[x],siz[y])<=k<=siz[x]+siz[y]，
然后就是合并成多少个小于号的方案数了，
1 #include<cstdio> 2 #include<algorithm> 3 #include<iostream> 4 #include<cstring> 5 #include<cmath> 6 #include<cstdlib> 7 #define N 107 8 #define M 207 9 #define mod 1000000007 10 #define ll long long 11 using namespace std; 12 13 int n,m,S; 14 int cnt,head[N],next[M],rea[M]; 15 int fa[N],du[N],siz[N]; 16 bool boo[N],hash[N]; 17 struct Node 18 { 19 int x,y; 20 }a[N]; 21 ll c[N][N],f[N][N],g[N],ans; 22 23 void add(int u,int v) 24 { 25 next[++cnt]=head[u]; 26 head[u]=cnt; 27 rea[cnt]=v,du[v]++; 28 } 29 int find(int num) 30 { 31 if (fa[num]!=num) fa[num]=find(fa[num]); 32 return fa[num]; 33 } 34 void dfs(int u,int fa) 35 { 36 boo[u]=1;bool flag=0; 37 for (int i=head[u];i!=-1;i=next[i]) 38 { 39 int v=rea[i]; 40 if (v==fa) continue; 41 dfs(v,u); 42 if (flag) 43 { 44 memset(g,0,sizeof(g)); 45 for (int i1=1;i1<=siz[u];i1++) 46 if (f[u][i1]) 47 for (int j1=1;j1<=siz[v];j1++) 48 if (f[v][j1]) 49 for (int k1=max(i1,j1);k1<=i1+j1;k1++) 50 g[k1]=(g[k1]+f[u][i1]*f[v][j1]%mod*c[k1][i1]%mod*c[i1][j1-(k1-i1)]%mod)%mod; 51 siz[u]+=siz[v]; 52 for (int i=1;i<=siz[u];i++) 53 f[u][i]=g[i]; 54 } 55 else 56 { 57 flag=1; 58 siz[u]=siz[v]; 59 for (int i=1;i<=siz[v];i++) 60 f[u][i]=f[v][i]; 61 } 62 } 63 if (u!=S) 64 { 65 siz[u]++;if (!flag) f[u][1]=1; 66 else for (int i=siz[u];i>=1;i--) f[u][i]=f[u][i-1]; 67 } 68 } 69 bool dfs_circle(int u) 70 { 71 for (int i=head[u];i!=-1;i=next[i]) 72 { 73 int v=rea[i]; 74 if (boo[v]) return false; 75 boo[v]=true; 76 if (!dfs_circle(v)) return false; 77 } 78 return true; 79 } 80 int main() 81 { 82 memset(head,-1,sizeof(head)); 83 scanf("%d%d",&n,&m); 84 for (int i=1;i<=n;i++) 85 fa[i]=i; 86 for (int i=0;i<=n;i++) 87 c[i][0]=1; 88 for (int i=1;i<=n;i++) 89 for (int j=1;j<=i;j++) 90 c[i][j]=(c[i-1][j]+c[i-1][j-1])%mod; 91 //======================================================================================== 92 int x,y,top=0;char ch[2]; 93 for (int i=1;i<=m;i++) 94 { 95 scanf("%d%s%d",&x,&ch,&y); 96 if (ch[0]=='=') 97 { 98 int u=find(x),v=find(y); 99 fa[v]=u; 100 continue; 101 } 102 else if (ch[0]=='>') swap(x,y); 103 a[++top].x=x,a[top].y=y; 104 } 105 m=top; 106 for (int i=1;i<=m;i++) 107 { 108 int u=find(a[i].x),v=find(a[i].y); 109 if (u!=v) add(u,v);//如果一个相等集合中有相互比较关系 110 else 111 { 112 printf("0 "); 113 return 0; 114 } 115 } 116 for (int i=1;i<=n;i++) 117 if (!boo[i]) 118 { 119 boo[i]=1; 120 if (!dfs_circle(i)) 121 { 122 printf("0 "); 123 return 0; 124 } 125 } 126 S=n+1; 127 for (int i=1;i<=n;i++) 128 { 129 int zhi=find(i); 130 if (!du[zhi]&&!hash[zhi]) 131 { 132 add(S,zhi); 133 hash[zhi]=1; 134 } 135 } 136 //========================================================================================= 137 dfs(S,-1); 138 for (int i=1;i<=siz[S];i++) 139 ans=(ans+f[S][i])%mod; 140 printf("%lld ",ans); 141 }