2018.12.28-dtoj-3648-寝室管理

#include<cstdio>
#include<cstring>
#include<iostream>
using namespace std;
typedef long long ll;
const int N=1e5+5,M=2e5+5;
int k,m,w,r,c,n,t[M],l[M],h[N],f[N],p[N],s[N],d[N];
bool b[N];ll a[N],q;
int get(int x){return !f[x]?x:f[x]=get(f[x]);}
void insert(int x,int y){
    t[++c]=y,l[c]=h[x],h[x]=c;
    t[++c]=x,l[c]=h[y],h[y]=c;
}
void add(int x,int y=1){
    for(;x<=n;x+=x&-x)
        if(p[x]!=c) p[x]=c,a[x]=y;
        else a[x]+=y;
    }
ll sum(int x){
    if(x<0) return 0;
    ll y=0;
    for(;x;x-=x&-x)
        if(p[x]==c) y+=a[x];
    return y;
}
#define z t[i]
void root(int x,int y){
    int c=0;s[x]=1;
    for(int i=h[x];i;i=l[i]){
        if(b[z] || y==z) continue;
        root(z,x);
        s[x]+=s[z];
        c=max(c,s[z]);
    }
    c=max(c,m-s[x]);
    if(c<w) w=c,r=x;
}
void dfs1(int x,int y,int w){
    s[x]=1;q+=sum(n)-sum(k-w-1);
    for(int i=h[x];i;i=l[i]){
        if(b[z] || y==z) continue;
        dfs1(z,x,w+1);s[x]+=s[z];
    }
}
void dfs2(int x,int y,int w){
    add(w+1);
    for(int i=h[x];i;i=l[i])
        if(!b[z] && y!=z) dfs2(z,x,w+1);
}
void solve(int x){
    ++c;b[x]=1;add(1);
    for(int i=h[x];i;i=l[i])
        if(!b[z]) dfs1(z,x,1),dfs2(z,x,1);
    for(int i=h[x];i;i=l[i]){
        if(b[z]) continue;
        w=1e9;m=s[z];
        root(z,x);solve(r);
    }
}
void dfs3(int x){
    add(d[x]);
    for(int i=h[x];i;i=l[i]){
        if(z==f[x]) continue;
        f[z]=x;d[z]=d[x]+1;
        dfs3(z);
    }
}
void dfs4(int x,int y){
    add(d[x],-1);
    for(int i=h[x];i;i=l[i])
        if(z!=y && !b[z]) dfs4(z,x);
}
void dfs5(int x,int y,int w){
    q+=sum(n)-sum(k-w-1);
    for(int i=h[x];i;i=l[i])
        if(z!=y && !b[z]) dfs5(z,x,w+1);
}
int main(){
    int x,y,u,v,g=0,h;
    scanf("%d%d%d",&n,&m,&k);
    while(m--){
        scanf("%d%d",&x,&y);
        u=get(x),v=get(y);
        if(u==v) g=x,h=y;
        else f[u]=v,insert(x,y);
    }
    c=0;m=n,w=1e9;
    root(1,0);
    solve(r);
    if(!g) return !printf("%lld\n",q);
    memset(b,0,n+1);
    ++c;f[g]=0;d[g]=1;dfs3(g);
    for(int i=h;i;i=f[i]) b[i]=1;
    for(int i=h,j=1;i!=g;i=f[i],++j) dfs4(i,0),dfs5(i,0,j);
    printf("%lld\n",q);
    return 0;
}