UVA - 11324 The Largest Clique 강연통 축소점 + 기억화 dp

/*
Tarjan            set        
Col           。
*/
#include <iostream>
#include<cstring>
#include<cstdio>
#include<string>
#include<algorithm>
using namespace std;
#define MAXN 2005
#define MAXM 100005
struct node
{
    int to,next;
}edge[MAXM],edge2[MAXM];
bool have[1005][1005];
int sums[1005];
int head[MAXN],head2[MAXN],en,en2;
bool root[MAXN];
int low[MAXN],dfn[MAXN],stack[MAXN],top,set[MAXN],col,num;
bool vis[MAXN],instack[MAXN];
int dp[MAXN];
int n;
int m;
void addedge(int a,int b)
{
    edge[en].to=b;
    edge[en].next=head[a];
    head[a]=en++;
}
void addedge2(int a,int b)
{
    edge2[en2].to=b;
    edge2[en2].next=head2[a];
    head2[a]=en2++;
}
void tarjan(int u)
{

    vis[u]=1;
    dfn[u]=low[u]=++num;
    instack[u]=true;
    stack[++top]=u;
    for(int i=head[u];i!=-1;i=edge[i].next)
    {
        int v=edge[i].to;
        if(!vis[v])
        {
            tarjan(v);
            low[u]=min(low[u],low[v]);
        }
        else
            if(instack[v])
                low[u]=min(dfn[v],low[u]);
    }
    if(dfn[u]==low[u])
    {
        int j;
        col++;
        do
        {
            j=stack[top--];
            instack[j]=false;
          set[j]=col;
        }
        while (j!=u);
    }
}
void init()
{
    int i;
    en=en2=top=col=num=0;
    memset(head,-1,sizeof(head));
    memset(head2,-1,sizeof(head2));
    memset(instack,0,sizeof(instack));
    memset(vis,0,sizeof(vis));
    memset(set,-1,sizeof(set));
    memset(have,0,sizeof(have));
    memset(sums,0,sizeof(sums));
    memset(root,true,sizeof(root));
    memset(dp,-1,sizeof(dp));
}
int ans;
int dfs(int now,int fa)
{
    if(~dp[now]) return dp[now];
    int maxs=sums[now];
    for(int i=head2[now];~i;i=edge2[i].next)
    {
        int to=edge2[i].to;
        if(to!=fa)
        {
            maxs=max(maxs,sums[now]+dfs(to,now));
        }
    }
    return dp[now]=maxs;
}
int main()
{
    int a,b;
    int cas;
    scanf("%d",&cas);
    while(cas--)
    {
        scanf("%d%d",&n,&m);
        init();
        for(int i=1;i<=m;i++)
        {
            scanf("%d%d",&a,&b);
            addedge(a,b);
        }
        for(int i=1;i<=n;i++)
            if(!vis[i])tarjan(i);
        for(int i=1;i<=n;i++)
        {
            sums[set[i]]++;
            for(int j=head[i];~j;j=edge[j].next)
            {
                int to=edge[j].to;
                if(set[i]!=set[to]&&!have[set[i]][set[to]])
                {
                    addedge2(set[i],set[to]);
                    root[set[to]]=false;
                    have[set[i]][set[to]]=have[set[to]][set[i]]=true;
                }
            }
        }
        ans=0;
        for(int i=1;i<=col;i++)
        {
            if(root[i])
            {
                dfs(i,-1);
                ans=max(ans,dp[i]);
            }
        }
        printf("%d
",ans);
    }
    return 0;
}