uva 11324 The Largest Clique(强连通分量缩点+DAG动态规划)

#include <stdio.h>
#include <string.h>
#include <algorithm>
#include <stack>
#include <vector>
#define LL long long
#define _LL __int64

using namespace std;
const int INF = 0x3f3f3f3f;
const int maxn = 1010;

vector <int> edge[maxn],edge2[maxn];
int n,m;
int dfn[maxn],low[maxn],instack[maxn],dep,scc;
stack <int> st;
int set[maxn],num[maxn];
int d[maxn];

void init()
{
for(int i = 1; i <= n; i++)
{
edge[i].clear();
edge2[i].clear();
}
memset(dfn,0,sizeof(dfn));
memset(low,0,sizeof(low));
memset(instack,0,sizeof(instack));
while(!st.empty()) st.pop();

dep = 0;
scc = 0;
memset(num,0,sizeof(num));
memset(d,0,sizeof(d));
}

void tarjan(int u)
{
dfn[u] = low[u] = ++dep;
instack[u] = 1;
st.push(u);

for(int i = 0; i < (int)edge[u].size(); i++)
{
int v = edge[u][i];
if(!dfn[v])
{
tarjan(v);
low[u] = min(low[u],low[v]);
}
else if(instack[v])
low[u] = min(low[u],dfn[v]);
}
if(dfn[u] == low[u])
{
scc++;
int t;
while(1)
{
t = st.top();
st.pop();
instack[t] = 0;
set[t] = scc;
num[scc]++;
if(t == u)
break;
}
}
}

void creat()
{
for(int u = 1; u <= n; u++)
{
for(int i = 0; i < (int)edge[u].size(); i++)
{
int v = edge[u][i];
if(set[u] != set[v])
edge2[set[u]].push_back(set[v]);
}
}
}

int dp(int u)
{
if(d[u]) return d[u];
else if(edge2[u].size() == 0) return d[u] = num[u];

int ans = 0;
for(int i = 0; i < (int)edge2[u].size(); i++)
{
int v = edge2[u][i];
ans = max(ans,dp(v));
}
return d[u] = ans+num[u];
}

int main()
{
int test,u,v;
scanf("%d",&test);
while(test--)
{
init();
scanf("%d %d",&n,&m);
for(int i = 1; i <= m; i++)
{
scanf("%d %d",&u,&v);
if(u == v) continue;
edge[u].push_back(v);
}
for(int i = 1; i <= n; i++)
if(!dfn[i])
tarjan(i);

creat();

int ans = 0;
for(int i = 1; i <= scc; i++)
{
ans = max(ans,dp(i));
}
printf("%d\n",ans);
}
return 0;
}