The Largest Clique UVA - 11324

#include <cstdio>
#include <iostream>
#include <algorithm>
#include <cstring>
#include <cmath>
#include <iostream>
#include <stack>
#define MAXN 50100
using namespace std;
struct edge{
    int first;
    int next;
    int to;
}a[MAXN*2];
int dfn[MAXN],in[MAXN],low[MAXN],fa[MAXN],size[MAXN];
int dp[MAXN],b[MAXN],x[MAXN],y[MAXN];
int n,m,num1=0,num2=0,num3=0;
stack<int> s;

void cl(){
    memset(low,0,sizeof(low));
    memset(dp,0,sizeof(dp));
    memset(dfn,0,sizeof(dfn));
    memset(fa,0,sizeof(fa));
    memset(size,0,sizeof(size));
    memset(a,0,sizeof(a));num1=num2=num3=0;
    memset(in,0,sizeof(in));
    memset(b,0,sizeof(b));
    memset(x,0,sizeof(x));
    memset(y,0,sizeof(y));
}

void addedge(int from,int to){
    a[++num1].to=to;
    a[num1].next=a[from].first;
    a[from].first=num1;
}

void init(){
    scanf("%d%d",&n,&m);
    for(int i=1;i<=m;i++){
        scanf("%d%d",&x[i],&y[i]);
        addedge(x[i],y[i]);
    }
}

void tarjian(int now){
    s.push(now);in[now]=1;
    dfn[now]=low[now]=++num3;
    for(int i=a[now].first;i;i=a[i].next){
        int to=a[i].to;
        if(!dfn[to]){
            tarjian(to);
            low[now]=min(low[now],low[to]);
        }
        else if(in[to]) low[now]=min(low[now],dfn[to]);
    }
    if(low[now]==dfn[now]){
        int u=-1;
        num2++;
        while(u!=now){
            u=s.top();s.pop();in[u]=0;
            fa[u]=num2;
            size[num2]++;
        }
    }
}

void make(){
    memset(a,0,sizeof(a));num1=0;
    for(int i=1;i<=m;i++){
        if(fa[x[i]]!=fa[y[i]]) addedge(fa[x[i]],fa[y[i]]);
    }
}

void pre(){
    while(!s.empty()) s.pop();
    for(int i=1;i<=n;i++) if(!dfn[i]) tarjian(i);
    make();
}

int DP(int now){
    if(b[now]) return dp[now];
    b[now]=1;
    dp[now]+=size[now];
    for(int i=a[now].first;i;i=a[i].next){
        int to=a[i].to;
        dp[now]=max(dp[now],size[now]+DP(to));
    }
    return dp[now];
}

int main()
{
    int t;cin>>t;
    while(t--){
        cl();
        init();
        pre();
        for(int i=1;i<=n;i++) DP(i);
        int ans=0;
        for(int i=1;i<=n;i++) ans=max(ans,dp[i]);
        printf("%d\n",ans);
    }
    return 0;
}