hdu 1317

最短路存在负环的问题。

#include<cstdio>#include<stack>#include<cstring>using namespace std;struct node{int to;int next;int w;node(){}node(int a,int b,int c):to(a),next(b),w(c){}}edge[100*100+10];int head[105];int dist[106];int  vis[106];int  cnt[106];int okay[105][106];int tot;void add_edge(int u,int v,int w){edge[tot] = node(v,head[u],w);head[u] = tot++;}void flody(int n){for(int k=1;k<=n;k++)for(int i=1;i<=n;i++)for(int j=1;j<=n;j++)okay[i][j] = okay[i][j]|(okay[i][k]&okay[k][j]);}void spfa(int n){stack<int>s;memset(vis,0,sizeof(vis));memset(cnt,0,sizeof(cnt));for(int i=1;i<=n;i++){dist[i] = -105;}dist[1] = 100;s.push(1);vis[1] = 1;int flag = 0;int d;while(!s.empty()){int u = s.top();s.pop();vis[u] = 0;cnt[u]++;if(cnt[u]>=n){d = u;flag = 1;break;}for(int i=head[u];i!=-1;i=edge[i].next){int v = edge[i].to;int w = edge[i].w;if(dist[v]<dist[u]+w&&dist[u]+w>0){dist[v] = dist[u]+w;if(!vis[v]){vis[v] = 1;s.push(v);}}}}if(flag==1){if(okay[d][n])printf("winnable\n");elseprintf("hopeless\n");return ;}if(dist[n]>0) printf("winnable\n");else printf("hopeless\n");}int main(){int n;while(scanf("%d",&n)){if(n==-1)break;int w,t,v;tot = 0;memset(head,-1,sizeof(head));memset(okay,0,sizeof(okay));for(int i=1;i<=n;i++){scanf("%d",&w);scanf("%d",&t);for(int j=0;j<t;j++){scanf("%d",&v);add_edge(i,v,w);okay[i][v] = 1;}}flody(n);if(!okay[1][n]){printf("hopeless\n");continue;}spfa(n);}return 0;}