51nod 1811 联通分量计数

竟然作死   lower_bound(s[u].begin(),s[u].end(),*it1); T的不明所以QAQ

#include<stdio.h>#include<string.h>#include<iostream>#include<algorithm>#include<set>#include<time.h>using namespace std;const int MAXN=(int)1e5+10;int read(){    int x=0,f=1;char ch=getchar();    while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}    while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}    return x*f;}typedef long long ll;struct edge{int to,nxt;}ed[MAXN<<1];int head[MAXN],cnt;void addedge(int u,int v){ed[cnt].to=v;ed[cnt].nxt=head[u];head[u]=cnt++;}struct node{int l,r;node(){}node(int _l,int _r){l=_l;r=_r;}bool operator < (const node &a)const{if(l==a.l)return r<a.r;else return l<a.l;}};set<node>s[MAXN];set<node>::iterator it1,it2,it3;int idx[MAXN];ll vl[MAXN],ans;int n;ll gx(ll x){return x*(x-1)/2;}void merge(int &u,int &v){if(s[u].size()<s[v].size())swap(u,v);for(it1=s[v].begin();it1!=s[v].end();it1++){it2=s[u].lower_bound(*it1);if(it2==s[u].end()){while(it1!=s[v].end()){it2=s[u].end();it2--;if(it1->l==it2->r+1){vl[u]-=gx(n-it2->r);vl[u]-=gx(it2->r-it2->l+1);vl[u]+=gx(it1->r-it2->l+1);vl[u]+=gx(n-it1->r);node nw=node(it2->l,it1->r);s[u].erase(it2);s[u].insert(nw);}else {vl[u]-=gx(n-it2->r);vl[u]+=gx(it1->l-it2->r-1);vl[u]+=gx(it1->r-it1->l+1);vl[u]+=gx(n-it1->r);s[u].insert(*it1);}it1++;}break;}else if(it2==s[u].begin()){if(it1->r+1==it2->l){vl[u]-=gx(it2->r-it2->l+1);vl[u]-=gx(it2->l-1);vl[u]+=gx(it1->l-1);vl[u]+=gx(it2->r-it1->l+1);node nw=node(it1->l,it2->r);s[u].erase(it2);s[u].insert(nw);}else {vl[u]-=gx(it2->l-1);vl[u]+=gx(it1->l-1);vl[u]+=gx(it1->r-it1->l+1);vl[u]+=gx(it2->l-it1->r-1);s[u].insert(*it1);}}else {it3=it2;it3--;if(it3->r+1==it1->l&&it1->r+1==it2->l){vl[u]-=gx(it2->r-it2->l+1)+gx(it3->r-it3->l+1)+gx(it1->r-it1->l+1);vl[u]+=gx(it2->r-it3->l+1);node nw=node(it3->l,it2->r);s[u].erase(it2);s[u].erase(it3);s[u].insert(nw);}else if(it3->r+1==it1->l){vl[u]-=gx(it2->l-it3->r-1);vl[u]-=gx(it3->r-it3->l+1);vl[u]+=gx(it1->r-it3->l+1);vl[u]+=gx(it2->l-it1->r-1);node nw=node(it3->l,it1->r);s[u].erase(it3);s[u].insert(nw);}else if(it1->r+1==it2->l){vl[u]-=gx(it2->l-it3->r-1);vl[u]-=gx(it2->r-it2->l+1);vl[u]+=gx(it1->l-it3->r-1);vl[u]+=gx(it2->r-it1->l+1);node nw=node(it1->l,it2->r);s[u].erase(it2);s[u].insert(nw);}else {vl[u]-=gx(it2->l-it3->r-1);vl[u]+=gx(it1->l-it3->r-1)+gx(it1->r-it1->l+1)+gx(it2->l-it1->r-1);s[u].insert(*it1);}}}}void dfs(int u,int pre){s[idx[u]].insert(node(u,u));vl[u]=gx(u-1)+gx(n-u);for(int i=head[u];i!=-1;i=ed[i].nxt){int v=ed[i].to;if(v!=pre){dfs(v,u);ans-=vl[idx[v]];merge(idx[u],idx[v]);}}}int main(){memset(head,-1,sizeof(head));n=read();for(int i=1;i<=n;i++)idx[i]=i;for(int i=1;i<n;i++){int u,v;u=read();v=read();addedge(u,v);addedge(v,u);}ans=1LL*n*(n-1)/2*(n-1);dfs(n/2+1,0);printf("%lld\n",ans);return 0;}