【HNOI2008】【洛谷P3196】【BZOJ1006】神奇的国度（弦图染色）（最大势）

BZOJ传送门

洛谷传送门

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懒得写题解了，CDQ论文里面都有证明和讲解。

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代码：

#include<bits/stdc++.h>
#define ll long long
#define re register
#define gc get_char
#define cs const

namespace IO{
	inline char get_char(){
		static cs int Rlen=1<<22|1;
		static char buf[Rlen],*p1,*p2;
		return (p1==p2)&&(p2=(p1=buf)+fread(buf,1,Rlen,stdin),p1==p2)?EOF:*p1++; 
	}
	
	template<typename T>
	inline T get(){
		char c;
		while(!isdigit(c=gc()));T num=c^48;
		while(isdigit(c=gc()))num=(num+(num<<2)<<1)+(c^48);
		return num;
	}
	inline int getint(){return get<int>();}
}
using namespace IO;

using std::cerr;
using std::cout;

cs int N=1e4+5;

int n,m;

struct LI{
	int id;
	LI *pre,*suf;
	inline void del(){
		pre->suf=suf;
		if(suf)suf->pre=pre;
	}
	inline void push(LI *p){
		p->pre=this;
		p->suf=suf;
		if(suf)suf->pre=p;
		suf=p;
	}
}head[N],p[N];

std::vector<int> G[N];

bool vis[N];
int nd[N],deg[N],pos[N];

inline void addedge(int u,int v){
	G[u].push_back(v);
	G[v].push_back(u);
}

inline void MSC(){
	for(int re i=1;i<=n;++i)head[0].push(&p[i]),p[i].id=i;
	int mxc=0;
	for(int re i=1;i<=n;++i){
		while(head[mxc+1].suf)++mxc;
		while(!head[mxc].suf)--mxc;
		int u=head[mxc].suf->id;
		nd[n-i+1]=u;vis[u]=true;pos[u]=n-i+1;
		head[mxc].suf->del();
		for(int re e=G[u].size()-1;~e;--e){
			int v=G[u][e];
			if(!vis[v]){
				p[v].del();
				head[++deg[v]].push(&p[v]);
			}
		}
	}
}

inline int mxset(){
	int ans=1;
	for(int re i=n;i;--i){
		int u=nd[i],cnt=1;
		for(int re e=G[u].size()-1;~e;--e){
			int v=G[u][e];
			if(pos[v]>pos[u])++cnt;
		}
		ans=std::max(ans,cnt); 
	}
	return ans;
}

signed main(){
//	freopen("country.in","r",stdin);//freopen("country.out","w",stdout);
	n=getint(),m=getint();
	for(int re i=1;i<=m;++i)addedge(getint(),getint());
	MSC();
	cout<<mxset()<<"\n"; 
	return 0;
}