hdu 3986 Harry Potter and the Final Battle spfa变形

来源：互联网发布：linux怎么禁ping 编辑：程序博客网时间：2024/06/05 20:41
#include<stdio.h>#include<string.h>#include<queue>#include<vector>using namespace std;const int N=1024;const int inf=0x7fffffff;struct Edge{    int u,v,w,use,del;};vector<Edge>edge;vector<int>G[N];int n,m,dist[N],inq[N],mp[N][N],path[N],d[N];void spfa(){    int i,u,v;    memset(inq,0,sizeof(inq));    memset(mp,0,sizeof(mp));    for(i=1;i<=n;i++)    {        dist[i]=inf;        path[i]=1;    }    dist[1]=0;    queue<int>q;    q.push(1);    inq[1]=1;    while(!q.empty())    {        u=q.front();        q.pop();        inq[u]=0;        for(i=0;i<G[u].size();i++)        {            int t=G[u][i];            if(edge[t].del) continue;            if(u==edge[t].u) v=edge[t].v;            else v=edge[t].u;            if(dist[v]>dist[u]+edge[t].w)            {                dist[v]=dist[u]+edge[t].w;                mp[u][v]=t;path[v]=u;                if(inq[v]==0)                {                    q.push(v);                    inq[v]=1;                }            }        }    }}int main(){    int _,i,j,u,v,w;    Edge tp;    scanf("%d",&_);    while(_--)    {        edge.clear();        for(i=0; i<1024; i++) G[i].clear();        scanf("%d",&n);        scanf("%d",&m);        for(i=0; i<m; i++)        {            scanf("%d%d%d",&u,&v,&w);            tp.u=u,tp.v=v,tp.w=w,tp.use=0,tp.del=0;            edge.push_back(tp);            G[u].push_back(i);            G[v].push_back(i);        }        spfa();        if(dist[n]==inf)            {printf("-1\n");continue;}        int k1=n,k2=path[n];        while(1)        {            edge[mp[k2][k1]].use=1;            if(k2==1) break;            k1=k2;            k2=path[k2];        }        int ans=-1;       for(i=0; i<m; i++)        {            if(edge[i].use)            {                edge[i].del=1;                spfa();                if(dist[n]==inf)                {                    ans=-1;break;                }                ans=max(ans,dist[n]);                edge[i].del=0;            }        }            printf("%d\n",ans);    }    return 0;}
0 0