zoj 2676 dinic模板求实型最小割（可做dinic模板）

#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\n",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\n",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\n",k);
            if(flow>eps)
                st=mid+eps;
            else
                en=mid-eps;
        }
  //      printf("mid=%.10f\n",mid);
        memset(vis,0,sizeof(vis));
        vis[1]=1;
        dfss(1);
        len=0;
            for(i=1;i<=m;i++) {
          //  printf("%.10f %.10f\n",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\n",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("\n");
            }
    return 0;
}