#include<stdio.h> #include<string.h> #include<stdlib.h> #include<queue> #include<math.h> using namespace std; #define eps 1e-6 #define inf 0x3fffffff #define N 410 struct node { int u,v,next; double w; }bian[N*4],f[N]; int yong,head[N],dis[N],work[N]; void init() { yong=0; memset(head,-1,sizeof(head)); } void addedge(int u,int v,double w) { bian[yong].v=v; bian[yong].w=w; bian[yong].next=head[u]; head[u]=yong++; } int bfs(int S,int T) { queue<int>q; memset(dis,-1,sizeof(dis)); dis[S]=0; q.push(S); while(!q.empty()) { int u=q.front(); q.pop(); for(int i=head[u];i!=-1;i=bian[i].next) { int v=bian[i].v; if(bian[i].w>0&&dis[v]==-1) { dis[v]=dis[u]+1; if(v==T) return 1; q.push(v); } } } return 0; } double dfs(int S,double a,int T) { if(S==T)return a; for(int &i=work[S];i!=-1;i=bian[i].next) { int v=bian[i].v; if(bian[i].w>0&&dis[v]==dis[S]+1) { double tt=dfs(v,min(a,bian[i].w),T); if(tt>0) { bian[i].w-=tt; bian[i^1].w+=tt; return tt; } } } return 0; } double Dinic(int S,int T) { double ans=0; while(bfs(S,T)) { memcpy(work,head,sizeof(head)); while(1) { double tt=dfs(S,inf,T);//割出来的可能是负值 if(tt<eps)break; ans+=tt; } } return ans; } int a[N],len,vis[N]; void dfss(int u) { int i; // printf("%d ",u); for(i=head[u];i!=-1;i=bian[i].next) { int v=bian[i].v; if(bian[i].w>eps&&!vis[v]) { vis[v]=1; dfss(v); } } } int main() { int n,m,i; double st,en,mid,flow; while(scanf("%d%d",&n,&m)!=EOF) { for(i=1; i<=m; i++) scanf("%d%d%lf",&f[i].u,&f[i].v,&f[i].w); st=0; en=10000001; while(st<en+eps) { mid=(st+en)/2; init(); flow=0; for(i=1; i<=m; i++) { // printf("%.2f %.2f ",f[i].w,mid); if(f[i].w<mid+eps) flow=flow+f[i].w-mid; else { addedge(f[i].u,f[i].v,f[i].w-mid); addedge(f[i].v,f[i].u,f[i].w-mid); } } double k=Dinic(1,n); flow+=k; // printf("%.2f ",k); if(flow>eps) st=mid+eps; else en=mid-eps; } // printf("mid=%.10f ",mid); memset(vis,0,sizeof(vis)); vis[1]=1; dfss(1); len=0; for(i=1;i<=m;i++) { // printf("%.10f %.10f ",f[i].w,mid+eps);//&&vis[f[i].u]+vis[f[i].v]==1 if(vis[f[i].u]+vis[f[i].v]==1||f[i].w<eps+mid) len++; } printf("%d ",len); int ok=0; for(i=1;i<=m;i++) if(vis[f[i].u]+vis[f[i].v]==1||f[i].w<mid+eps) { if(ok) printf(" "); printf("%d",i); ok=1; } printf(" "); } return 0; }