BZOJ 2834: 回家的路 Dijkstra

按照横，竖为方向跑一个最短路即可，算是水题~

#include <bits/stdc++.h>
#define N 200005
#define E 2000000
#define setIO(s) freopen(s".in","r",stdin)
using namespace std;
int n,m,tot,edges,s,T;
int hd[E],to[E],nex[E],val[E],d[E],done[E],id[E][2];
void addedge(int u,int v,int c)
{
    nex[++edges]=hd[u],hd[u]=edges,to[edges]=v,val[edges]=c;
}
struct Point
{
    int x,y,id;
    Point(int x=0,int y=0):x(x),y(y){}
}t[N];
struct Node
{
    int u,dis;
    Node(int u=0,int dis=0): u(u),dis(dis){}
    bool operator<(Node b) const
    {
        return b.dis<dis;
    }
};
priority_queue<Node>q;
bool cmpx(Point a,Point b)
{
    return a.x==b.x?a.y<b.y:a.x<b.x;
}
bool cmpy(Point a,Point b)
{
    return a.y==b.y?a.x<b.x:a.y<b.y;
}
void Dijkstra()
{
    memset(d,0x3f,sizeof(d));
    for(d[s]=0, q.push(Node(s, 0)); !q.empty(); )
    {
        Node e = q.top(); q.pop();
        int u=e.u;
        if(done[u]) continue;
        done[u]=1;
        for(int i=hd[u];i;i=nex[i])
        {
            int v=to[i];
            if(d[v] > d[u] + val[i])
            {
                d[v] = d[u] + val[i];
                q.push(Node(v, d[v]));
            }
        }
    }
}
int main()
{
    int i,j,k;
    // setIO("input");
    scanf("%d%d",&n,&m);
    for(i=2;i<=m+1;++i)
    {
        scanf("%d%d",&t[i].x,&t[i].y);
        id[i][0]=++tot;
        id[i][1]=++tot;
        t[i].id=i;
    }
    scanf("%d%d",&t[1].x,&t[1].y);
    id[1][0]=++tot;
    id[1][1]=++tot;
    t[1].id=1;
    m+=2;
    scanf("%d%d",&t[m].x,&t[m].y);
    id[m][0]=++tot;
    id[m][1]=++tot;
    t[m].id=m;
    for(i=1;i<=m;++i)
    {
        addedge(id[i][0],id[i][1],1);
        addedge(id[i][1],id[i][0],1);
    }
    sort(t+1,t+1+m,cmpx);
    for(i=1;i<=m;i=j)
    {
        for(j=i;j<=m&&t[j].x==t[i].x;++j);
        for(k=i+1;k<j;++k)
        {
            addedge(id[t[k-1].id][1], id[t[k].id][1], 2 * (t[k].y-t[k-1].y));
            addedge(id[t[k].id][1], id[t[k-1].id][1], 2 * (t[k].y-t[k-1].y));
        }
    }
    sort(t+1,t+1+m,cmpy);
    for(i=1;i<=m;i=j)
    {
        for(j=i;j<=m&&t[j].y==t[i].y;++j);
        for(k=i+1;k<j;++k)
        {
            addedge(id[t[k-1].id][0], id[t[k].id][0], 2 * (t[k].x-t[k-1].x));
            addedge(id[t[k].id][0], id[t[k-1].id][0], 2 * (t[k].x-t[k-1].x));
        }
    }  

    s=0, T=++tot;    

    addedge(s, id[1][0], 0);
    addedge(s, id[1][1], 0);   

    addedge(id[m][0], T, 0);
    addedge(id[m][1], T, 0);
    Dijkstra();
    printf("%d\n",d[T]);
    return 0;
}