BZOJ 4152: [AMPPZ2014]The Captain Dijkstra+贪心

Code:

#include <queue>
#include <cstdio>
#include <cstring>
#include <algorithm>
#define N 400005
#define ll long long
#define setIO(s) freopen(s".in","r",stdin)
using namespace std;
ll d[N];
int n,edges;
int hd[N],to[N<<1],nex[N<<1],val[N<<1],done[N];
void addedge(int u,int v,int c)
{
    nex[++edges]=hd[u],hd[u]=edges,to[edges]=v,val[edges]=c;
    swap(u,v);
    nex[++edges]=hd[u],hd[u]=edges,to[edges]=v,val[edges]=c;
}
struct Point
{
    int x,y,id;
}e[N];
bool cmpx(Point a,Point b)
{
    return a.x<b.x;
}
bool cmpy(Point a,Point b)
{
    return a.y<b.y;
}
struct Node
{
    int u;
    ll dis;
    Node(int u=0,ll dis=0):u(u),dis(dis){}
    bool operator<(Node b) const
    {
        return b.dis<dis;
    }
};
priority_queue<Node>q;
void Dijkstra()
{
    int s=1;
    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,i,v;
        if(done[u]) continue;
        done[u]=1;
        for(i=hd[u];i;i=nex[i])
        {
            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",&n);
    for(i=1;i<=n;++i)
    {
        int x,y;
        scanf("%d%d",&e[i].x,&e[i].y), e[i].id=i;
    }
    sort(e+1,e+1+n,cmpx);
    for(i=2;i<=n;++i)
        addedge(e[i-1].id,e[i].id,e[i].x-e[i-1].x);
    sort(e+1,e+1+n,cmpy);
    for(i=2;i<=n;++i)
    {
        addedge(e[i-1].id,e[i].id,e[i].y-e[i-1].y);
    }
    Dijkstra();
    printf("%lld\n",d[n]);
    return 0;
}