【[CTSC2000]冰原探险】

noip前练一下码力还是非常有前途的

这道题本来就是想写个大暴力弃疗的，所以直接强上暴力浑身舒爽

结果发现要不是判重的时候脑残了，就能\(A\)了

没什么好说的呀，就是每一次都暴力\(O(n)\)往上下左右扩展状态，之后放到队列里，\(map\)判重就好了

代码

#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<queue>
#include<map>
#include<cstring>
#define mp std::make_pair
#define re register
#define maxn 4005
#define min(a,b) ((a)<(b)?(a):(b))
#define max(a,b) ((a)>(b)?(a):(b))
inline int read()
{
	char c=getchar();
	int x=0,r=1;
	while(c<'0'||c>'9') {if(c=='-') r=-1;c=getchar();}
	while(c>='0'&&c<='9')
		x=(x<<3)+(x<<1)+c-48,c=getchar();
	return x*r;
}
struct node
{
	int x,y,step;
};
std::map<std::pair<int,int> ,bool > vis;
inline void GG()
{
	puts("0");
	exit(0);
}
inline void kill(int a)
{
	printf("%d\n",a);
	exit(0);
}
int ix[maxn],iy[maxn],Ix[maxn],Iy[maxn];
int n,sx,sy,dx,dy;
inline void BFS()
{
	std::queue<node> q;
	q.push((node){sx,sy,0});
	vis[mp(sx,sy)]=1;
	while(!q.empty())
	{
		node mid=q.front();
		q.pop();
		int xx=mid.x,yy=mid.y;

		int pre=-99999999;
		for(re int i=1;i<=n;i++)
			if(yy>=iy[i]&&yy<=Iy[i]&&Ix[i]<=xx) pre=max(pre,Ix[i]);
		if(pre!=-99999999)
		{
			if(pre!=xx&&!vis[mp(pre+1,yy)])
			{
				vis[mp(pre+1,yy)]=1,q.push((node){pre+1,yy,mid.step+1});
				if(dy==yy&&dx<xx&&xx>=pre+1) kill(mid.step+1);
			}
		}
		else if(dy==yy&&dx<xx) kill(mid.step+1);

		pre=999999999;
		for(re int i=1;i<=n;i++)
			if(yy>=iy[i]&&yy<=Iy[i]&&ix[i]>=xx) pre=min(pre,ix[i]);
		if(pre!=999999999)
		{
			if(pre!=xx&&!vis[mp(pre-1,yy)])
			{
				vis[mp(pre-1,yy)]=1,q.push((node){pre-1,yy,mid.step+1});
				if(dy==yy&&dx>xx&&xx<=pre-1) kill(mid.step+1);
			}
		}
		else if(dy==yy&&dx>xx) kill(mid.step+1);

		pre=-99999999;
		for(re int i=1;i<=n;i++)
			if(xx>=ix[i]&&xx<=Ix[i]&&Iy[i]<=yy) pre=max(pre,Iy[i]);
		if(pre!=-99999999)
		{
			if(pre!=yy&&!vis[mp(xx,pre+1)])
			{
				vis[mp(xx,pre+1)]=1,q.push((node){xx,pre+1,mid.step+1});
				if(dx==xx&&dy<yy&&dy>=pre+1) kill(mid.step+1);
			}
		}
		else if(dx==xx&&dy<yy) kill(mid.step+1);

		pre=99999999;
		for(re int i=1;i<=n;i++)
			if(xx>=ix[i]&&xx<=Ix[i]&&iy[i]>=yy) pre=min(pre,iy[i]);
		if(pre!=99999999)
		{
			if(pre!=yy&&!vis[mp(xx,pre-1)])
			{
				vis[mp(xx,pre-1)]=1,q.push((node){xx,pre-1,mid.step+1});
				if(dx==xx&&dy>yy&&dy<=pre-1) kill(mid.step+1);;
			}
		}
		else if(dx==xx&&dy>yy) kill(mid.step+1);
	}
	GG();
}
int main()
{
	n=read();
	sx=read(),sy=read(),dx=read(),dy=read();
	for(re int i=1;i<=n;i++) ix[i]=read(),iy[i]=read(),Ix[i]=read(),Iy[i]=read();
	BFS();
	return 0;
}