tarjan后dp
常规操作求最长路
#include<cstdio>
#include<iostream>
#include<algorithm>
#include<map>
#define LL long long
const int maxn = 5000007;
inline int read()
{
int x=0,f=1;
char c=getchar();
while(c<'0' || c>'9') {if (c=='-') f=-1; c=getchar();}
while(c>='0' && c<='9') {x=x*10+c-'0'; c=getchar();}
return x*f;
}
struct data{
int x,y,id,opt;
}a[maxn];
struct edge{
int to,next;
}edge[maxn<<2],E[maxn];
int head[maxn],H[maxn>>1],cnt,recnt,ind,top,n,x,y;
bool inq[maxn],vis[maxn>>1];
int ans;
int q[maxn],dfn[maxn],low[maxn];
int size[maxn>>1],belong[maxn],tot;
bool cmp_x(data a,data b) {
return a.x<b.x;
}
bool cmp_y(data a,data b) {
return a.y<b.y;
}
void add_edge(int x, int y) {
edge[++cnt].to=y; edge[cnt].next=head[x]; head[x]=cnt;
}
void Add_edge(int x, int y) {
E[++recnt].to=y; E[recnt].next=H[x]; H[x]=recnt;
}
void tarjan(int x) {
q[++top]=x; dfn[x]=low[x]=++ind;
inq[x]=1;
for(int i=head[x];i;i=edge[i].next)
if(!dfn[edge[i].to]) {
tarjan(edge[i].to);
low[x]=std::min(low[x],low[edge[i].to]);
}
else if (inq[edge[i].to]) low[x]=std::min(low[x],dfn[edge[i].to]);
int now=-1;
if(dfn[x]==low[x]) {
tot++;
while(now!=x) {
now=q[top--];
belong[now]=tot;
size[tot]++;
inq[now]=0;
}
}
}
void dfs(int x) {
vis[x]=1;int mx=0;
for(int i=H[x];i;i=E[i].next){
if(!vis[E[i].to])
dfs(E[i].to);
mx=std::max(size[E[i].to],mx);
}
ans=std::max(ans,size[x]+=mx);
}
std::map<LL,int>GG;
int main() {
n=read();x=read();y=read();
for (int i=1; i<=n; i++) a[i].x=read(),
a[i].y=read(),a[i].opt=read(),GG[(LL)a[i].x*maxn+a[i].y]=i,a[i].id=i;
std::sort(a+1,a+n+1,cmp_x);
for(int i=1;i<=n;i++)
if(a[i].opt==1) {
for (int j=i-1;j>=1; j--)
if (a[i].x==a[j].x) add_edge(a[i].id,a[j].id);
else break;
for (int j=i+1; j<=n; j++)
if (a[i].x==a[j].x) add_edge(a[i].id,a[j].id);
else break;
}
std::sort(a+1,a+n+1,cmp_y);
for(int i=1;i<=n;i++)
if(a[i].opt==2)
{
for(int j=i-1;j>=1;j--)
if(a[i].y==a[j].y)
add_edge(a[i].id,a[j].id);
else break;
for(int j=i+1;j<=n;j++)
if(a[i].y==a[j].y)
add_edge(a[i].id,a[j].id);
else break;
}
for(int i=1;i<=n;i++)
if(a[i].opt==3){
for(int j=a[i].x-1; j<=a[i].x+1; j++)
for(int k=a[i].y-1; k<=a[i].y+1; k++)
if(j!=a[i].x||k!=a[i].y)
if(GG[(LL)j*maxn+k])
add_edge(a[i].id,GG[(LL)j*maxn+k]);
}
for(int i=1; i<=n; i++)
if(!dfn[i])tarjan(i);
for(int x=1;x<=n;x++)
for(int i=head[x];i;i=edge[i].next)
if(belong[x]!=belong[edge[i].to])
Add_edge(belong[x],belong[edge[i].to]);
for(int i=1;i<=tot;i++)
if(!vis[i]) dfs(i);
printf("%d
",ans);
return 0;
}