P3831 [SHOI2012]回家的路

思路

很简单 分层图 + (SPFA)

坑点

我提交了(10+)次 全部(90pts)

希望各位大佬不会跟我犯一样的错误

空间大小不要开错了

不然会(WA) 而不是(RE) 半天差不出来错的那种（第二个点一直错）

点 开 (3e5 + 10)

边开 (3e6 + 10)

这题没有卡(SPFA)

不用堆优化 （374ms）在题解中算挺快的

不用开(long long)

(Code)

#include <stack>
#include <queue>
#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
using namespace std;
#define reg register int
#define isdigit(x) ('0' <= x&&x <= '9')
template<typename T>
inline T Read(T Type)
{
	T x = 0,f = 1;
	char a = getchar();
	while(!isdigit(a)) {if(a == '-') f = -1;a = getchar();}
	while(isdigit(a)) {x = (x << 1) + (x << 3) + (a ^ '0');a = getchar();}
	return x * f;
}
const int MAXN = 3e5 + 10,MAXM = 3e6 + 10;
struct node
{
	int x,y,num;
}sta[MAXN];
bool cmp1(node a,node b)
{
	if(a.x < b.x) return 1;
	if(a.x == b.x) return (a.y < b.y?1:0);
	return 0;
}
bool cmp2(node a,node b)
{
	if(a.y < b.y) return 1;
	if(a.y == b.y) return (a.x < b.x?1:0);
	return 0;
}
inline int cost(int a,int b) {return (a - b > 0?a - b:b - a) * 2;}
struct EDGE
{
	int u,v,w,next;
}edge[MAXM];
int n,m,cnt,head[MAXN];
inline void addedge(int u,int v,int w)
{
	edge[++cnt].u = u;
	edge[cnt].v = v;
	edge[cnt].w = w;
	edge[cnt].next = head[u];
	head[u] = cnt;
}
inline void add(int u,int v,int w) {addedge(u,v,w),addedge(v,u,w);}
inline void buildgraph()
{
	sort(sta + 1,sta + 3 + m,cmp1);
	for(reg i = 2;i <= m + 2;i++)
		if(sta[i].x == sta[i - 1].x) 
			add(sta[i].num,sta[i - 1].num,cost(sta[i - 1].y,sta[i].y));
	sort(sta + 1,sta + 3 + m,cmp2);
	for(reg i = 2;i <= m + 2;i++)
		if(sta[i].y == sta[i - 1].y) 
			add(sta[i].num + m + 2,sta[i - 1].num + m + 2,cost(sta[i - 1].x,sta[i].x));
	for(reg i = 1;i <= m + 2;i++)
		add(sta[i].num,sta[i].num + m + 2,(sta[i].num > m?0:1));
}
bool vis[MAXN];
int d[MAXN];
inline int dijkstra(int s,int t)
{
	queue<int> q;
	q.push(s);
	vis[s] = 1;
	memset(d,0x7f7f7f,sizeof(d));
	d[s] = 0;
	while(!q.empty())
	{
		int tp = q.front();q.pop();
		vis[tp] = 0;
		for(reg e = head[tp];e;e = edge[e].next)
		{
			int v = edge[e].v,w = edge[e].w;
			if(d[tp] + w < d[v])
			{
				d[v] = d[tp] + w;
				if(!vis[v]) q.push(v);
				vis[v] = 1;
			}
		}
	}
	return (d[t] < 0x7f7f7f?d[t]:-1);
}
int main()
{
	n = Read(1),m = Read(1);
	for(reg i = 1;i <= m + 2;i++)
		sta[i].x = Read(1),sta[i].y = Read(1),sta[i].num = i;
	buildgraph();
	int ans = dijkstra(m + 1,m + 2);
	printf("%d",ans);
	return 0;
}