POJ2607/ZOJ1857 (最短路...注意题意及输入控制)

题目链接:  http://poj.org/problem?id=2607

               http://acm.zju.edu.cn/onlinejudge/showProblem.do?problemId=857

 

其实啥都不想说,万恶的题意,万恶到输入都不给说明...

 

minimize the maximum distance from any intersection to the nearest fire station.

好吧, 这一句把我绕得~看了别人的才知道是这么个状况,加入的fire station不是为整个city服务

而是为了几个别complaint的村庄而计划的,,,

 

上代码,注释都赖得写了:

　zoj24733752011-04-04 14:20:24Accepted 1857C++10500zzuli_ㄉㄉ

   poj

128429467dooder_daodao232K47MSC++2229B2011-04-04 14:06:07

 

#include<cstdio>#include<cstring>#include<queue>using namespace std;#define M 508#define N 20008#define INF 0x7ffffffftypedef struct talQNode{int v,c;bool operator < (const talQNode &a) const{return a.c<c;}}QNode;typedef struct{int u,v,c;int next;}Edge;Edge edge[N];int head[M];int dis[M],disl[M];bool vis[M],inq[M];int fire[M];int f,n,e;priority_queue<QNode>q;void AddEdge(int u,int v,int c){edge[e].u=u;edge[e].v=v;edge[e].c=c;edge[e].next=head[u];head[u]=e++;edge[e].v=u;edge[e].u=v;edge[e].c=c;edge[e].next=head[v];head[v]=e++;}void Dijkstra(int f){QNode cur,next;int u,v,tmp;memset(vis,false,n+1);cur.v=f;cur.c=0;q.push(cur);while(!q.empty()){cur=q.top();q.pop();u=cur.v;if(vis[u]) continue;dis[u]=cur.c;vis[u]=true;for(tmp=head[u];tmp!=-1;tmp=edge[tmp].next){v=edge[tmp].v;if(vis[v]) continue;if(dis[v]-dis[u]>edge[tmp].c){dis[v]=dis[u]+edge[tmp].c;next.v=v;next.c=dis[v];q.push(next);}}}}int SPFA(int f){QNode cur,next;int rel,u,v,tmp;memset(inq,false,n+1);cur.v=f;cur.c=0;inq[f]=true;disl[f]=0;q.push(cur);while(!q.empty()){cur=q.top();q.pop();u=cur.v;inq[u]=false;for(tmp=head[u];tmp!=-1;tmp=edge[tmp].next){v=edge[tmp].v;if(disl[v]-disl[u]>edge[tmp].c){disl[v]=disl[u]+edge[tmp].c;if(!inq[v]){inq[v]=true;next.v=v;next.c=disl[v];q.push(next);}}}}rel=0;for(int i=1;i<=n;i++){if(disl[i]>rel)rel=disl[i];}return rel;}void InitDis(){int i;for(i=0;i<=n;i++)dis[i]=INF;for(i=0;i<f;i++)Dijkstra(fire[i]);}int Find(){int ret=0,i,min=INF,tmp;for(i=1;i<=n;i++){memmove(disl,dis,4*(n+1));tmp=SPFA(i);if(tmp<min){ret=i;min=tmp;}}return ret;}int main(){int i,u,v,c;char s[108];while(~scanf("%d%d",&f,&n)){memset(head,-1,sizeof(head));e=0;for(i=0;i<f;i++)scanf("%d",fire+i);getchar();while(gets(s)&&s[0]){sscanf(s,"%d%d%d",&u,&v,&c);AddEdge(u,v,c);}InitDis();printf("%d/n",Find());}return 0;}