cf1066F Yet Another 2D Walking (贪心+dijkstra)

易证我们走的时候只会从某一层的某端点走向另一端点、然后走向下一层的某端点..

所以建图然后dijkstra就行了

调了一年以后发现dijkstra写错了

 #include<bits/stdc++.h>
 #define pa pair<ll,int>
 #define CLR(a,x) memset(a,x,sizeof(a))
 using namespace std;
 typedef long long ll;
 const int maxn=4e5+;
 const ll inf=1e18;

 inline ll rd(){
     ll x=;char c=getchar();int neg=;
     while(c<''||c>''){if(c=='-') neg=-;c=getchar();}
     while(c>=''&&c<='') x=x*+c-'',c=getchar();
     return x*neg;
 }

 struct Edge{
     int b,ne;ll l;
 }eg[maxn*];
 struct Node{
     ll x,y,l;
 }pos[maxn];
 int N,egh[maxn],ect;
 ll dd[maxn];
 bool flag[maxn];
 priority_queue<pa,vector<pa>,greater<pa> > q;

 inline bool cmp(Node a,Node b){return a.l<b.l;}
 inline void adeg(int a,int b,ll l){
     eg[++ect].b=b;eg[ect].ne=egh[a];eg[ect].l=l;egh[a]=ect;
 }
 inline ll dis(int a,int b){return abs(pos[a].x-pos[b].x)+abs(pos[a].y-pos[b].y);}

 void dijkstra(){
     CLR(dd,-);
     dd[+N]=;q.push(make_pair(,+N));
     while(!q.empty()){
         int p=q.top().second;q.pop();
         if(flag[p]) continue;
         flag[p]=;
         for(int i=egh[p];i;i=eg[i].ne){
             int b=eg[i].b;
             if(dd[b]==-||dd[b]>dd[p]+eg[i].l){
                 dd[b]=dd[p]+eg[i].l;
                 q.push(make_pair(dd[b],b));
             }
         }
     }
 }

 int main(){
     //freopen(".in","r",stdin);
     int i,j,k;
     N=rd();
     for(i=;i<=N;i++)
         pos[i].x=rd(),pos[i].y=rd(),pos[i].l=max(pos[i].x,pos[i].y);
     pos[N+].x=,pos[N+].y=,pos[N+].l=;
     N++;
     sort(pos+,pos+N+,cmp);
     int lst1=-,lst2=-;
     int la=-,lb=-;
     for(i=N,j=N,k=N;i;i){
         int aa=-,bb=-;
         for(;pos[j].l==pos[i].l&&j;j--){
             if(aa==-||pos[j].x<pos[aa].x||(pos[j].x==pos[aa].x&&pos[j].y>pos[aa].y)) aa=j;
             if(bb==-||pos[j].y<pos[bb].y||(pos[j].y==pos[bb].y&&pos[j].x>pos[bb].x)) bb=j;
         }
         if(lst1==-) lst1=aa;
         if(lst2==-) lst2=bb;
         if(la!=-) adeg(aa+N,la,dis(la,aa)),adeg(bb+N,la,dis(la,bb));
         if(lb!=-) adeg(aa+N,lb,dis(lb,aa)),adeg(bb+N,lb,dis(lb,bb));
         adeg(aa,bb+N,dis(aa,bb));adeg(bb,aa+N,dis(aa,bb));
         la=aa,lb=bb;
     }
     dijkstra();
     printf("%I64d\n",min(dd[lst1+N],dd[lst2+N]));
     return ;
 }