codeforces 449B Jzzhu and Cities (Dij+堆优化)

输入一个无向图<V,E>    V<=1e5, E<=3e5

现在另外给k条边(u=1,v=s[k],w=y[k])

问在不影响从结点1出发到所有结点的最短路的前提下，最多可以删除k条边的多少条

跑最短路的时候维护或者统计就好了

一开始用spfa.然后TLE 45...好久没写  Dij+堆优化   ...

p.s.优先队列默认大顶堆

Dij+堆优化   264ms

 #include <cstdio>
 #include <cstring>
 #include <iostream>
 #include <algorithm>
 #include <cmath>
 #include <queue>
 #include <set>
 #include <string>
 using namespace std;

 #define ll long long
 #define maxn 100010
 #define maxm 700010

 int head[maxn];
 struct edge{
     int v,w,nxt;
 }e[maxm];
 int E;
 void init(){E=;memset(head,-,sizeof(head));}
 void addedge(int u,int v,int w){
     e[E].v=v,e[E].w=w,e[E].nxt=head[u];
     head[u]=E++;
 }
 priority_queue<pair<ll,int> >que;
 bool vis[maxn];
 //ll d[maxn];
 int main(){
     int n,m,k;
     while(~scanf("%d%d%d",&n,&m,&k)){
         init();
         for(int i=;i<m;++i){
             int u,v,w;
             scanf("%d%d%d",&u,&v,&w);
             addedge(u,v,w);
             addedge(v,u,w);
         }
         que.push(make_pair(0ll,));
         for(int i=;i<k;++i){
             int s,y;
             scanf("%d%d",&s,&y);
             que.push(make_pair(0ll-y,-s));
         }
         memset(vis,false,sizeof(vis));
         int ans=;
         while(!que.empty()){
             pair<ll,int> tmp = que.top();que.pop();
             ll dis = -tmp.first;
             int u = tmp.second;
             if(u<){
                 u=-u;
                 if(vis[u])++ans;
             }
             if(vis[u]) continue;
             vis[u]=true;
             //d[u] = dis;
             for(int i=head[u];i!=-;i=e[i].nxt)
                 if(vis[e[i].v]==false)
                     que.push(make_pair( -dis-e[i].w, e[i].v));
         }
         printf("%d\n",ans);
     }
     return ;
 }

spfa  TLE 45

 #include <cstdio>
 #include <cstring>
 #include <iostream>
 #include <algorithm>
 #include <cmath>
 #include <queue>
 #include <set>
 #include <string>
 using namespace std;

 #define ll long long
 #define maxn 100010
 #define maxm 700010

 int head[maxn];
 struct edge{
     int v,w,nxt;
     int k;
 }e[maxm];
 int E;
 void init(){E=;memset(head,-,sizeof(head));}
 void addedge(int u,int v,int w,int kind){
     e[E].v=v,e[E].w=w,e[E].nxt=head[u];
     e[E].k = kind;
     head[u]=E++;
 }
 int q[maxn];
 bool inq[maxn];
 bool bus[maxn];
 ll dis[maxn];
 void spfa(){
     int hd=,tl=;
     q[tl++]=;
     memset(dis,0x3f,sizeof(dis));
     dis[]=;
     memset(inq,false,sizeof(inq));
     inq[]=true;
     memset(bus,false,sizeof(bus));
     while(hd!=tl){
         int u = q[hd++];
         if(hd==maxn)hd=;
         inq[u] = false;
         for(int i=head[u];i!=-;i=e[i].nxt){
             int v = e[i].v, w = e[i].w, k = e[i].k;
             if(dis[u]+w < dis[v]){
                 dis[v] = dis[u]+w;
                 bus[v] = false;
                 if(k==) bus[v]=true;
                 if(inq[v]==false){
                     inq[v]=true;
                     q[tl++]=v;
                     if(tl==maxn)tl=;
                 }
             }else if(dis[u]+w == dis[v]){
                 if(k==) bus[v]=true;
             }
         }
     }
 }
 int si[],yi[];
 int main(){
     int n,m,k;
     while(~scanf("%d%d%d",&n,&m,&k)){
         init();
         for(int i=;i<m;++i){
             int u,v,w;
             scanf("%d%d%d",&u,&v,&w);
             addedge(u,v,w,);
             addedge(v,u,w,);
         }
         for(int i=;i<k;++i){
             scanf("%d%d",si+i,yi+i);
             addedge(,si[i],yi[i],);
         }
         spfa();
         int ans=;
         for(int i=;i<k;++i){
             int v = si[i];
             if(dis[v] < yi[i]) ++ans;
             else {
                 if(bus[v]==false)bus[v]=true;
                 else ++ans;
             }
         }
         printf("%d\n",ans);
     }
     return ;
 }