50 lines
1.0 KiB
C++
50 lines
1.0 KiB
C++
#include<cstdio>
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#include<cstring>
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#include<algorithm>
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#include<vector>
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using namespace std;
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const int maxn=205;
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int n,m;
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vector<int> G[maxn],E[maxn];
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double a[maxn][maxn],res=0;
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void solve(int mi)
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{
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memset(a,0,sizeof(a));
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int md=1<<mi;
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for(int i=1;i<n;i++)
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{
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a[i][i]=G[i].size();
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for(int j=0;j<G[i].size();j++)
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if(E[i][j]&md)
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{
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a[i][n+1]=a[i][n+1]+1;
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a[i][G[i][j]]=a[i][G[i][j]]+1;
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}
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else a[i][G[i][j]]=a[i][G[i][j]]-1;
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}
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a[n][n]=1; a[n][n+1]=0;
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for(int i=1;i<=n;i++)
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{
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for(int j=i;j<=n;j++) if(a[j][i]!=0) { for(int k=1;k<=n+1;k++) swap(a[i][k],a[j][k]); break; }
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for(int j=n+1;j>=i;j--) a[i][j]/=a[i][i];
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for(int j=1;j<=n;j++) if(j!=i) for(int k=n+1;k>=i;k--) a[j][k]-=a[j][i]*a[i][k];
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}
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res+=md*a[1][n+1];
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}
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int main()
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{
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#ifdef local
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freopen("pro.in","r",stdin);
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#endif
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scanf("%d%d",&n,&m);
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for(int i=0;i<m;i++)
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{
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int u,v,w; scanf("%d%d%d",&u,&v,&w);
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G[u].push_back(v); E[u].push_back(w);
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if(u!=v) { G[v].push_back(u); E[v].push_back(w); }
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}
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for(int i=0;i<30;i++)
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solve(i);
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printf("%.3lf\n",res);
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return 0;
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} |