[线段树优化建图最短路 bfs] BZOJ 3073 [Pa2011]Journeys

CA爷的题解：http://blog.youkuaiyun.com/CreationAugust/article/details/50739132

#include<cstdio>
#include<cstdlib>
#include<algorithm>
#include<set>
using namespace std;

inline char nc()
{
	static char buf[100000],*p1=buf,*p2=buf;
	if (p1==p2) { p2=(p1=buf)+fread(buf,1,100000,stdin); if (p1==p2) return EOF; }
	return *p1++;
}

inline void read(int &x)
{
	char c=nc(),b=1;
	for (;!(c>='0' && c<='9');c=nc()) if (c=='-') b=-1;
	for (x=0;c>='0' && c<='9';x=x*10+c-'0',c=nc()); x*=b;
}

const int N=500005;

struct edge{
	int l,r;
	int next;
}G[10*N];

int inum,head[4*N];

inline void add(int rt,int l,int r,int p){
	G[p].l=l; G[p].r=r; G[p].next=head[rt]; head[rt]=p;
}

int M;

inline void Build(int n){
	for (M=1;M<n+2;M<<=1);
}

inline void insert(int s,int t,int a,int b)
{
	for (s+=M-1,t+=M+1;s^t^1;s>>=1,t>>=1)
	{
		if (~s&1) add(s^1,a,b,++inum);
		if ( t&1) add(t^1,a,b,++inum);
	}
}

int n,m,P;
int dis[N];

int Q[N],l,r;
//set<int> Set;
//typedef set<int>::iterator ITER;
int Stk[N],pnt;

int fat[N];
int Fat(int u){
	return u==fat[u]?u:fat[u]=Fat(fat[u]);
}

int main()
{
	int a,b,c,d,u;
//	ITER it;
	freopen("t.in","r",stdin);
	freopen("t.out","w",stdout); 
	read(n); read(m); read(P); 
	Build(n);
	for (int i=1;i<=m;i++)
	{
		read(a); read(b); read(c); read(d);
		insert(a,b,c,d); insert(c,d,a,b);
	}
	l=r=-1; Q[++r]=P; dis[P]=0;
//	for (int i=1;i<=n;i++) if (i!=P) Set.insert(i);
	for (int i=1;i<=n+1;i++) fat[i]=i; 
	fat[P]=P+1;
	while (l<r)
	{
		int u=Q[++l]; 
		for (int t=M+u;t;head[t]=0,t>>=1)
			for (int p=head[t];p;p=G[p].next)
			{
//				for (pnt=0,it=Set.lower_bound(G[p].l);it!=Set.end() && *it<=G[p].r;it++)
//					dis[*it]=dis[u]+1,Q[++r]=*it,Stk[++pnt]=*it;
				pnt=0;
				for (int i=Fat(G[p].l);i<=G[p].r;i=Fat(i+1))
					dis[i]=dis[u]+1,Q[++r]=i,Stk[++pnt]=i;
//				while (pnt) Set.erase(Stk[pnt--]);
				while (pnt) fat[Stk[pnt]]=Stk[pnt]+1,pnt--;
			}
	}
	for (int i=1;i<=n;i++) printf("%d\n",dis[i]);
	return 0;