orz yyc

Posted 2020-10-27 kong-ruo

#include<bits/stdc++.h>
#define LL long long
using namespace std;
LL ans;
const int maxn = 100010;
int n,m,k,tot,C;
inline int read(){int x;scanf("%d",&x);return x;}
int first[maxn],to[maxn],next[maxn],cnt;
int root,sum;
int f[maxn],size[maxn],vis[maxn];
int q[maxn],dis[maxn],inq[maxn],inc[maxn],top;
inline void insert(int u,int v)
{
    to[++cnt] = v;
    next[cnt] = first[u];
    first[u] = cnt;
}

namespace Fenwick_Tree
{
    int c[maxn];
    inline int lowbit(int x){return x & (-x);}
    inline int query(int x)
    {
        if(x<1)return 0;
        int ret = 0;
        for(int i=x;i;i-=lowbit(i))ret += c[i];
        return ret;
    }
    inline void add(int x,int val)
    {
        tot += val;
        for(int i=x;i<=2*C+n;i+=lowbit(i))c[i] += val;
    }
}
using namespace Fenwick_Tree;
namespace DFZ
{
    inline void getrt(int x,int fa)
    {
        f[x] = 0;size[x] = 1;
        for(int i=first[x];i;i=next[i])
        {
            if(to[i] == fa || vis[to[i]])continue;
            getrt(to[i],x);
            size[x] += size[to[i]];
            f[x] = max(f[x],size[to[i]]);
        }
        f[x] = max(f[x],sum - size[x]);
        if(f[x] < f[root]) root  = x;
    }
    inline void dfs(int x,int fa)
    {
        q[++top] = dis[x];
        for(int i=first[x];i;i=next[i])
        {
            if(to[i] == fa || vis[to[i]])continue;
            dis[to[i]] = dis[x] + 1;
            dfs(to[i],x);
        }
    }
    inline void solve(int x)
    {
        vis[x] = 1;
        for(int i=first[x];i;i=next[i])
            if(!vis[to[i]])
            {
                dis[to[i]] = 1;
                dfs(to[i],x);
                for(int j=1;j<=top;j++)
                {
                    if(q[j] + 1 >= k)ans++;
                    ans += tot - query(k - q[j] - 2);
                }
                while(top) add(q[top--],1);
            }
        for(int i=first[x];i;i=next[i])
            if(!vis[to[i]])
            {
                dfs(to[i],x);
                while(top)add(q[top--],-1);
            }
        for(int i=first[x];i;i=next[i])
            if(!vis[to[i]] && size[to[i]] >= k)
            {
                root = 0;sum = size[to[i]];
                getrt(to[i],x);
                solve(root);
            }
    }
    inline void mian(int x)
    {
        sum = n;
        f[0] = 1e9;
        root = 0;
        getrt(x,0);
        solve(root);
    }
}
int INC,delta;
using namespace DFZ;
namespace inccle
{
    inline void getinc(int x,int fa)
    {
        if(INC) return;
        q[++top] = x , inq[x] = 1;
        for(int i=first[x];i;i=next[i])
        {
            if(to[i] == fa)continue;
            if(inq[to[i]])
            {
                while(q[top] != to[i])inc[++INC] = q[top--];
                inc[++INC] = to[i];
            }
            else getinc(to[i],x);
        }
        top--,inc[x] = 0;
    }
    void solveinc()
    {
        getinc(1,0);top=0;
        C=INC;delta=2*C;
        for(int i=1;i<=C;i++)inc[i+C]=inc[i];
        for(int i=1;i<=C;i++)vis[inc[i]]=1;
        for(int i=1;i<=C;i++)
        {
            vis[inc[i]]=0;
            mian(inc[i]);
            vis[inc[i]]=1;
        }
        for(int i=1;i<=n;i++)vis[i]=0;
        for(int i=1;i<=C;i++)vis[inc[i]]=1;
        for(int i=1;i<=2*C;i++)
        {
            if(i>C)
            {
                vis[inc[i-C]]=0;dfs(inc[i-C],0);vis[inc[i-C]]=1;
                for(int j=1;j<=top;j++)add(q[j]+delta+C,-1);
                for(int j=1;j<=top;j++)
                    ans+=tot-query(k+delta-q[j]);
                top=0;
            }
            dis[inc[i]]=1;
            vis[inc[i]]=0;dfs(inc[i],0);vis[inc[i]]=1;
            while(top)add(q[top--]+delta,1);delta--;
        }
    }
}
using namespace inccle;
int main()
{
    n=read();m=read();k=read();
    for(int i=1;i<=m;i++)
    {
        int u=read(),v=read();
        insert(u,v);
    }
    if(n==m)solveinc();
    else mian(1);
    printf("%lld\n",ans);
    return 0;
}

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