uva 10806 从一个点到另外1个点的2条不重复边的路径

#include<cstdio>#include<cstring>#include<queue>#define INF 0x3f3f3f3fusing namespace std;int g[160][160],vis[160],d[160],n,q,pre[160],res;int spfa(int s,int t){queue<int> q;memset(vis,0,sizeof(vis));memset(d,0x3f,sizeof(d));d[s]=0;vis[s]=1;q.push(s);while(!q.empty()){int u=q.front();q.pop();vis[u]=0;for(int i=1;i<=n;i++){if(d[i]>d[u]+g[u][i]){d[i]=d[u]+g[u][i];pre[i]=u;if(!vis[i]){vis[i]=1;q.push(i);}}}}if(d[t] == INF)return 0;for(int i=t;i!=s;i=pre[i]){res+=g[pre[i]][i];g[i][pre[i]]=-g[pre[i]][i];g[pre[i]][i]=INF;}return 1;}int main(){while(scanf("%d",&n) == 1 && n){res=0;memset(g,0x3f,sizeof(g));scanf("%d",&q);for(int i=0;i<q;i++){int u,v,c;scanf("%d%d%d",&u,&v,&c);g[u][v]=g[v][u]=c;}if(spfa(1,n) && spfa(1,n))printf("%d\n",res);elseprintf("Back to jail\n");}}