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
",d[n]);  
    return 0;    
}