【bzoj2834】回家的路 分层图最短路

#include <cstdio>
#include <cstring>
#include <utility>
#include <queue>
#include <algorithm>
using namespace std;
queue<pair<int , int> > q;
struct data
{
	int x , y , pos;
}a[100010];
int head[100010] , to[800010] , next[800010] , cnt , inq[100010][2];
long long len[800010] , dis[100010][2];
bool cmpx(data a , data b)
{
	return a.x == b.x ? a.y < b.y : a.x < b.x;
}
bool cmpy(data a , data b)
{
	return a.y == b.y ? a.x < b.x : a.y < b.y;
}
bool cmpp(data a , data b)
{
	return a.pos < b.pos;
}
void add(int x , int y , long long z)
{
	to[++cnt] = y;
	len[cnt] = z;
	next[cnt] = head[x];
	head[x] = cnt;
}
int main()
{
	int n , m , i , tx , p;
	pair<int , int> u;
	scanf("%d%d" , &n , &m);
	for(i = 1 ; i <= m ; i ++ )
		scanf("%d%d" , &a[i].x , &a[i].y);
	scanf("%d%d%d%d" , &a[0].x , &a[0].y , &a[m + 1].x , &a[m + 1].y);
	for(i = 0 ; i <= m + 1 ; i ++ )
		a[i].pos = i;
	sort(a , a + m + 2 , cmpx);
	for(i = 0 ; i <= m ; i ++ )
		if(a[i].x == a[i + 1].x)
			add(a[i].pos , a[i + 1].pos , 2 * (a[i + 1].y - a[i].y)) , add(a[i + 1].pos , a[i].pos , 2 * (a[i + 1].y - a[i].y));
	sort(a , a + m + 2 , cmpy);
	for(i = 0 ; i <= m ; i ++ )
		if(a[i].y == a[i + 1].y)
			add(a[i].pos , a[i + 1].pos , 2 * (a[i + 1].x - a[i].x)) , add(a[i + 1].pos , a[i].pos , 2 * (a[i + 1].x - a[i].x));
	sort(a , a + m + 2 , cmpp);
	memset(dis , 0x3f , sizeof(dis));
	dis[0][0] = dis[0][1] = 0;
	inq[0][0] = inq[0][1] = 1;
	q.push(make_pair(0 , 0));
	q.push(make_pair(0 , 1));
	while(!q.empty())
	{
		u = q.front();
		q.pop();
		tx = u.first;
		p = u.second;
		inq[tx][p] = 0;
		for(i = head[tx] ; i ; i = next[i])
		{
			if(!p && a[tx].x == a[to[i]].x || p && a[tx].y == a[to[i]].y)
			{
				if(dis[to[i]][p] > dis[tx][p] + len[i])
				{
					dis[to[i]][p] = dis[tx][p] + len[i];
					if(!inq[to[i]][p]) inq[to[i]][p] = 1 , q.push(make_pair(to[i] , p));
				}
			}
			if(p && a[tx].x == a[to[i]].x || !p && a[tx].y == a[to[i]].y)
			{
				if(dis[to[i]][p ^ 1] > dis[tx][p] + len[i] + 1)
				{
					dis[to[i]][p ^ 1] = dis[tx][p] + len[i] + 1;
					if(!inq[to[i]][p ^ 1]) inq[to[i]][p ^ 1] = 1 , q.push(make_pair(to[i] , p ^ 1));
				}
			}
		}
	}
	printf("%lld
" , min(dis[m + 1][0] , dis[m + 1][1]) == 0x3f3f3f3f3f3f3f3fll ? -1 : min(dis[m + 1][0] , dis[m + 1][1]));
	return 0;
}