概率与期望

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#define maxnode 20005
#define maxn 105
#define up 30
using namespace std;
struct use{
    double num[maxn];
}a[maxn],b;
int point[maxn]={0},next[maxnode]={0},en[maxnode]={0},va[maxnode][50]={0},tot=0,
    mi[50]={0},du[maxn]={0},n;
void add(int u,int v,int w)
{
    int i=0,x;
    ++tot;next[tot]=point[u];point[u]=tot;en[tot]=v;
    x=w;i=0;
    while(x) {va[tot][++i]=x%2;x/=2;}
    if (u==v) return;
    ++tot;next[tot]=point[v];point[v]=tot;en[tot]=u;
    x=w;i=0;
    while(x) {va[tot][++i]=x%2;x/=2;}
}
void gauss()
{
    int i,j,k;double t;
    for (i=1;i<=n;++i)
    {
        if (a[i].num[i]==0)
           for (j=i+1;j<=n;++j)
              if (a[j].num[i]!=0){swap(a[i],a[j]);break;}
        for (j=i+1;j<=n;++j)
        {
            t=a[j].num[i]*1.0/a[i].num[i];
            for (k=1;k<=n+1;++k) a[j].num[k]-=a[i].num[k]*t;
        }
    }
    for (i=n;i>=1;--i)
    {
        b.num[i]=a[i].num[n+1]*1.0/a[i].num[i];
        for (j=i-1;j>=1;--j)
        {
            a[j].num[n+1]-=b.num[i]*a[j].num[i];
            a[j].num[i]=0;
        }
    }
}
int main()
{
    int i,j,m,u,v,w,t;double ans=0;
    mi[1]=1;
    for (i=2;i<=up;++i) mi[i]=mi[i-1]*2;
    scanf("%d%d",&n,&m);
    for (i=1;i<=m;++i)
    {
        scanf("%d%d%d",&u,&v,&w);add(u,v,w);
        ++du[u];if (u!=v) ++du[v];
    }
    for (t=1;t<=up;++t)
    {
      memset(a,0,sizeof(a));
      memset(b.num,0,sizeof(b.num));
      for (i=1;i<n;++i)
      {
        a[i].num[i]=-du[i];
        for (j=point[i];j;j=next[j])
        {
            if (va[j][t]==0) ++a[i].num[en[j]];
            else
            {
                --a[i].num[en[j]];--a[i].num[n+1];
            }
        }
      } a[n].num[n]=1;
      gauss();ans+=b.num[1]*mi[t];
    }
    printf("%.3f\n",ans);
}