BZOJ3772精神污染

参见http://blog.csdn.net/popoqqq/article/details/43122821

 #include<bits/stdc++.h>
 using namespace std;
 typedef long long ll;
 const int N=1e5+;
 ll ans;int n,m,idx,cnt,head[N],tmp,rt[N],f[N][],d[N],in[N],out[N];
 vector<int>p[N];
 struct tree
 {
     int w,l,r;
 }t[];
 struct node
 {
     int x,y;
 }q[N];
 bool cmp(node a,node b)
 {
     return a.x==b.x?a.y<b.y:a.x<b.x;
 }
 struct edge
 {
     int to,nex;
 }e[N<<];
 void add(int x,int y)
 {
     e[++cnt].to=y;e[cnt].nex=head[x];head[x]=cnt;
 }
 void change(int &x,int y,int l,int r,int p,int w)
 {
     if(x==y||!x)x=++tmp,t[x]=t[y];
     if(l==r){
         t[x].w+=w;return;
     }
     int mid=l+r>>;
     if(p<=mid)change(t[x].l,t[y].l,l,mid,p,w);
     else change(t[x].r,t[y].r,mid+,r,p,w);
     t[x].w=t[t[x].l].w+t[t[x].r].w;
 }
 void dfs(int x)
 {
     in[x]=++idx;
     for(int i=;i<;++i)f[x][i]=f[f[x][i-]][i-];
     for(int i=head[x];i;i=e[i].nex)
     {
         int y=e[i].to;
         if(y==f[x][])continue;
         d[y]=d[x]+;f[y][]=x;
         dfs(y);
     }
     out[x]=++idx;
     return;
 }
 void dfs2(int x)
 {
     for(int i=;i<p[x].size();++i)
     {
         change(rt[x],rt[f[x][]],,*n,in[p[x][i]],);
         change(rt[x],rt[f[x][]],,*n,out[p[x][i]],-);
     }
     if(!p[x].size())rt[x]=rt[f[x][]];
     for(int i=head[x];i;i=e[i].nex)
     {
         int y=e[i].to;
         if(y==f[x][])continue;
         dfs2(y);
     }
 }
 int query(int rt1,int rt2,int rt3,int rt4,int l,int r,int L,int R)
 {
     if(l==L&&r==R)return t[rt1].w+t[rt2].w-t[rt3].w-t[rt4].w;//线段树动态开点
     int mid=l+r>>;
     if(R<=mid)return query(t[rt1].l,t[rt2].l,t[rt3].l,t[rt4].l,l,mid,L,R);
     else if(L>mid)return query(t[rt1].r,t[rt2].r,t[rt3].r,t[rt4].r,mid+,r,L,R);
     else return query(t[rt1].l,t[rt2].l,t[rt3].l,t[rt4].l,l,mid,L,mid)+query(t[rt1].r,t[rt2].r,t[rt3].r,t[rt4].r,mid+,r,mid+,R);
 }
 int lca(int x,int y)
 {
     if(d[x]<d[y])swap(x,y);
     int tt=d[x]-d[y];
     for(int i=;i<;++i)
     if(tt&(<<i))x=f[x][i];
     for(int i=;i>=;--i)
     if(f[x][i]!=f[y][i])
     {
         x=f[x][i];y=f[y][i];
     }
     return x==y?x:f[x][];
 }
 ll gcd(ll a,ll b)
 {
     return b==?a:gcd(b,a%b);
 }
 int main()
 {
     scanf("%d%d",&n,&m);
     int x,y,z;
     for(int i=;i<n;++i)
     {
         scanf("%d%d",&x,&y);
         add(x,y);add(y,x);
     }
     for(int i=;i<=m;++i)
     {
         scanf("%d%d",&q[i].x,&q[i].y);
         if(q[i].x>q[i].y)swap(q[i].x,q[i].y);
         p[q[i].x].push_back(q[i].y);
     }
     dfs();dfs2();
     for(int i=;i<=m;++i)
     {
         x=q[i].x,y=q[i].y,z=lca(x,y);
         ans+=query(rt[x],rt[y],rt[z],rt[f[z][]],,*n,in[z],in[x]);
         ans+=query(rt[x],rt[y],rt[z],rt[f[z][]],,*n,in[z],in[y]);
         ans-=query(rt[x],rt[y],rt[z],rt[f[z][]],,*n,in[z],in[z]);
         ans--;
     }
     sort(q+,q++m,cmp);
     for(int i=,j=i+;i<=m;i=j,j=i+)
     {
         while(j<=m&&q[i].x==q[j].x&&q[i].y==q[j].y)++j;
         ans-=1ll*(j-i)*(j-i-)/;
     }
     ll b=1ll*m*(m-)/,Gcd=gcd(ans,b);
     printf("%lld/%lld\n",ans/Gcd,b/Gcd);
     return ;
 }